Ever wondered why you can't throw exceptions from __toString()? Yeah me too.
Well now you can! This trick allows you to throw any type of exception from within a __toString(), with a full & correct backtrace.
How does it work? Well PHP __toString() handling is not as strict in every case: throwing an Exception from __toString() triggers a fatal E_ERROR, but returning a non-string value from a __toString() triggers a non-fatal E_RECOVERABLE_ERROR.
Add a little bookkeeping, and can circumvented this PHP deficiency!
(tested to work PHP 5.3+)
<?php
set_error_handler(array('My_ToStringFixer', 'errorHandler'));
error_reporting(E_ALL | E_STRICT);
class My_ToStringFixer
{
protected static $_toStringException;
public static function errorHandler($errorNumber, $errorMessage, $errorFile, $errorLine)
{
if (isset(self::$_toStringException))
{
$exception = self::$_toStringException;
// Always unset '_toStringException', we don't want a straggler to be found later if something came between the setting and the error
self::$_toStringException = null;
if (preg_match('~^Method .*::__toString\(\) must return a string value$~', $errorMessage))
throw $exception;
}
return false;
}
public static function throwToStringException($exception)
{
// Should not occur with prescribed usage, but in case of recursion: clean out exception, return a valid string, and weep
if (isset(self::$_toStringException))
{
self::$_toStringException = null;
return '';
}
self::$_toStringException = $exception;
return null;
}
}
class My_Class
{
public function doComplexStuff()
{
throw new Exception('Oh noes!');
}
public function __toString()
{
try
{
// do your complex thing which might trigger an exception
return $this->doComplexStuff();
}
catch (Exception $e)
{
// The 'return' is required to trigger the trick
return My_ToStringFixer::throwToStringException($e);
}
}
}
$x = new My_Class();
try
{
echo $x;
}
catch (Exception $e)
{
echo 'Caught Exception! : '. $e;
}
?>
Magische Methoden
Die Funktionen __construct(), __destruct(), __call(), __callStatic(), __get(), __set(), __isset(), __unset(), __sleep(), __wakeup(), __toString(), __invoke(), __set_state(), __clone() und __debugInfo() sind in PHP-Klassen magisch. Man kann keine Funktionen gleichen Namens in einer seiner Klassen haben, wenn man nicht die magische Funktionalität, die sie mit sich bringen, haben will.
Achtung
PHP reserviert alle Funktionsnamen, die mit __ beginnen, als magisch. Es wird empfohlen, keine Funktionsnamen mit __ in PHP zu benutzen, es sei denn, man möchte dokumentierte magische Funktionalität verwenden.
__sleep() and __wakeup()
public array __sleep
( void
)
void __wakeup
( void
)
serialize() prüft, ob Ihre Klasse eine Funktion mit dem
magischen Namen __sleep() besitzt. Wenn
dem so ist, wird die Funktion vor jeder Serialisierung ausgeführt. Sie kann
das Objekt aufräumen und es wird von ihr erwartet, dass sie ein Array mit den
Namen aller Variablen zurückliefert, die serialisiert werden sollen. Wenn die
Methode nichts zurückgibt, so wird NULL serialisiert und eine
E_NOTICE geworfen.
Hinweis:
__sleep() kann nicht Namen von privaten Eigenschaften von Elternklassen zurückgeben. In diesem Fall wird eine
E_NOTICEgeworfen. Stattdessen sollte das Serializable Interface verwendet werden.
Die beabsichtigte Verwendung von __sleep() ist, nicht gespeicherte Daten zu sichern oder ähnliche Aufräumarbeiten zu erledigen. Die Funktion ist ebenfalls nützlich, wenn Sie sehr große Objekte haben, welche nicht komplett gespeichert werden müssen.
Umgekehrt überprüft unserialize() die Anwesenheit einer Funktion mit dem magischen Namen __wakeup(). Falls vorhanden, kann diese Funktion alle Ressourcen, die das Objekt haben könnte, wiederherstellen.
Der beabsichtigte Zweck von __wakeup() ist es, alle Datenbankverbindungen wiederherzustellen, die während der Serialisierung verloren gegangen sein könnten, oder auch andere Aufgaben zur erneuten Initialisierung.
Beispiel #1 Sleep- und Wakeup-Beispiel
<?php
class Connection
{
protected $link;
private $dsn, $username, $password;
public function __construct($dsn, $username, $password)
{
$this->dsn = $dsn;
$this->username = $username;
$this->password = $password;
$this->connect();
}
private function connect()
{
$this->link = new PDO($this->dsn, $this->username, $this->password);
}
public function __sleep()
{
return array('dsn', 'username', 'password');
}
public function __wakeup()
{
$this->connect();
}
}?>
__toString()
public string __toString
( void
)
Die __toString() Methode erlaubt
einer Klasse zu entscheiden, wie sie reagieren soll, wenn sie in eine Zeichenkette
umgewandelt wird. Die beeinflusst beispielsweise, was echo $obj;
ausgeben wird. Diese Methode muss eine Zeichenkette zurückgeben, ansonsten wird ein
E_RECOVERABLE_ERROR geworfen.
Warnung
Aus der Methode __toString() kann keine Exception geworfen werden. Wenn dies getan wird, so tritt ein fataler Fehler auf.
Beispiel #2 Einfaches Beispiel
<?php
// Deklariere eine einfache Klasse
class TestClass
{
public $foo;
public function __construct($foo)
{
$this->foo = $foo;
}
public function __toString()
{
return $this->foo;
}
}
$class = new TestClass('Hallo');
echo $class;
?>
Das oben gezeigte Beispiel erzeugt folgende Ausgabe:
Hallo
Es muss angemerkt werden, dass die __toString()
Methode in Versionen vor PHP 5.2.0 nur in direkter Kombination mit
echo oder print aufgerufen
wurde.
Beginnend mit PHP 5.2.0 erfolgt dieser Aufruf in jedem Stringkontext
(z.B. in printf() mit %s-Platzhalter),
aber in keinem der anderen Typenkontexte (z.B. mit dem
%d-Platzhalter). Ebenfalls beginnend mit PHP 5.2.0
bewirkt die Umwandlung eines Objekts ohne __toString()
Methode in einen String einen Fehler der Klasse E_RECOVERABLE_ERROR.
__invoke()
Die __invoke()-Methode wird aufgerufen, wenn ein Skript versucht, ein Objekt als Funktion aufzurufen.
Hinweis:
Dieses Feature ist ab PHP 5.3.0 verfügbar.
Beispiel #3 Nutzung von __invoke()
<?php
class CallableClass
{
function __invoke($x)
{
var_dump($x);
}
}
$obj = new CallableClass;
$obj(5);
var_dump(is_callable($obj));
?>
Das oben gezeigte Beispiel erzeugt folgende Ausgabe:
int(5) bool(true)
__set_state()
static object __set_state
( array
$properties
)Diese statische Methode wird seit PHP 5.1.0 für Klassen aufgerufen, die mittels var_export() exportiert werden.
Der einzige Parameter dieser Methode ist ein Array, welches aus exportierten Eigenschaften der Form array('Eigenschaft' => Wert, ...) besteht.
Beispiel #4 Verwendung von __set_state() (seit PHP 5.1.0)
<?php
class A
{
public $var1;
public $var2;
public static function __set_state($an_array) // seit PHP 5.1.0
{
$obj = new A;
$obj->var1 = $an_array['var1'];
$obj->var2 = $an_array['var2'];
return $obj;
}
}
$a = new A;
$a->var1 = 5;
$a->var2 = 'foo';
eval('$b = ' . var_export($a, true) . ';'); // $b = A::__set_state(array(
// 'var1' => 5,
// 'var2' => 'foo',
// ));
var_dump($b);
?>
Das oben gezeigte Beispiel erzeugt folgende Ausgabe:
object(A)#2 (2) {
["var1"]=>
int(5)
["var2"]=>
string(3) "foo"
}
__debugInfo()
array __debugInfo
( void
)
Diese Methode wird von var_dump() aufgerufen, wenn ein Objekt ausgegeben wird, um die Eigenschaften auszulesen die gezeigt werden sollen. Wenn diese Methode in einem Objekt nicht definiert ist, so werden alle Eigenschaften die public, protected oder private sind angezeigt.
Diese Feature wurde mit PHP 5.6.0 hinzugefügt.
Beispiel #5 Verwendung von __debugInfo()
<?php
class C {
private $prop;
public function __construct($val) {
$this->prop = $val;
}
public function __debugInfo() {
return [
'propSquared' => $this->prop ** 2,
];
}
}
var_dump(new C(42));
?>
Das oben gezeigte Beispiel erzeugt folgende Ausgabe:
object(C)#1 (1) {
["propSquared"]=>
int(1764)
}
add a note
User Contributed Notes 42 notes
daan dot broekhof at gmail dot com ¶
2 years ago
staff at pro-unreal dot de ¶
1 year ago
To avoid instanciating the parent instead of the inherited class for __set_state() as reported by jsnell, you could use late static binding introduced in PHP 5.3:
<?php
class A {
public static function __set_state($data) {
return new static();
}
}
class B extends A {
}
$instance = new B();
eval('$test = ' . var_export($instance, true) . ';');
var_dump($test);
// -> object(B)#2 (0) {
// }
?>
krisj1010 at gmail.com ¶
10 years ago
If you are attempting to write an abstract/base class which automates the __sleep process in PHP5 you will run into some trouble if the subclasses which are being serialized have private/protected variables you need to be serialized.
The reason is, even though get_class($this) within the base class will return the subclass -- get_class_vars(get_class($this)) will *not* return the subclass' protected/private variables. Which makes sense -- using OO principles.
However, when automating __sleep it becomes necissary to have access to the private/protected subclass variables because their names have to be returned by __sleep.
So here is the work around:
<?php
public function __sleep()
{
... code ...
$sleepVars = array_keys((array)$this);
return $sleepVars;
}
?>
Even though array_keys includes more information about the variable names than just the variable names -- it still seems to work appropriately.
andrew dot minerd at sellingsource dot com ¶
7 years ago
Until __sleep is "fixed" (here's hoping), a function that will return ALL members of a given object -- public, protected, AND private:
<?php
public function getPropertyNames(array $filter = NULL)
{
$rc = new ReflectionObject($this);
$names = array();
while ($rc instanceof ReflectionClass)
{
foreach ($rc->getProperties() as $prop)
{
if (!$filter || !in_array($prop->getName(), $filter))
$names[] = $prop->getName();
}
$rc = $rc->getParentClass();
}
return $names;
}
?>
amir_abiri at ipcmedia dot com ¶
7 years ago
Another small thing that is important to note about __sleep() and privte member variables:
<?php
class A
{
private $a;
public function __construct()
{
$this->a = 1;
}
}
class B extends A
{
protected $b;
public function __construct()
{
parent::__construct();
$this->b = 2;
}
function __sleep()
{
return array('a', 'b');
}
}
serialize(new B);
?>
result:
Notice: serialize(): "a" returned as member variable from __sleep() but does not exist in ...
To summerize: in a given class hierarchy in which parent classes contain private member variables, those variables are serialized when __sleep() is not defined. However, once __sleep() is defined, there is no way to make those private member variables serialized as well. From that point on, serialization is performed from the visibility scope of the subclass.
It is particularly important to note this little quirk when designing base classes that their derivables may be serialized, or when subclassing an external library class.
jsnell at e-normous dot com ¶
6 years ago
Be very careful to define __set_state() in classes which inherit from a parent using it, as the static __set_state() call will be called for any children. If you are not careful, you will end up with an object of the wrong type. Here is an example:
<?php
class A
{
public $var1;
public static function __set_state($an_array)
{
$obj = new A;
$obj->var1 = $an_array['var1'];
return $obj;
}
}
class B extends A {
}
$b = new B;
$b->var1 = 5;
eval('$new_b = ' . var_export($b, true) . ';');
var_dump($new_b);
/*
object(A)#2 (1) {
["var1"]=>
int(5)
}
*/
?>
dhuseby domain getback tld com ¶
6 years ago
The above hint for using array_keys((array)$obj) got me investigating how to get __sleep to really work with object hierarchies.
With PHP 5.2.3, If you want to serialize an object that is part of an object hierarchy and you want to selectively serialize members (public, private, and protected) by manually specifying the array of members, there are a few simple rules for naming members that you must follow:
1. public members should be named using just their member name, like so:
<?php
class Foo {
public $bar;
public function __sleep() {
return array("bar");
}
}
?>
2. protected members should be named using "\0" . "*" . "\0" . member name, like so:
<?php
class Foo {
protected $bar;
public function __sleep() {
return array("\0*\0bar");
}
}
?>
3. private members should be named using "\0" . class name . "\0" . member name, like so:
<?php
class Foo {
private $bar;
public function __sleep() {
return array("\0Foo\0bar");
}
}
?>
So with this information let us serialize a class hierarchy correctly:
<?php
class Base {
private $foo = "foo_value";
protected $bar = "bar_value";
public function __sleep() {
return array("\0Base\0foo", "\0*\0bar");
}
}
class Derived extends Base {
public $baz = "baz_value";
private $boo = "boo_value";
public function __sleep() {
// we have to merge our members with our parent's
return array_merge(array("baz", "\0Derived\0boo"), parent::__sleep());
}
}
class Leaf extends Derived {
private $qux = "qux_value";
protected $zaz = "zaz_value";
public $blah = "blah_value";
public function __sleep() {
// again, merge our members with our parent's
return array_merge(array("\0Leaf\0qux", "\0*\0zaz", "blah"), parent::__sleep());
}
}
// test it
$test = new Leaf();
$s = serialize($test);
$test2 = unserialize($s);
echo $s;
print_r($test);
print_r($test2);
?>
Now if you comment out all of the __sleep() functions and output the serialized string, you will see that the output doesn't change. The most important part of course is that with the proper __sleep() functions, we can unserialize the string and get a properly set up object.
I hope this solves the mystery for everybody. __sleep() does work, if you use it correctly :-)
hyponiq at gmail dot com ¶
3 years ago
I think it's fair to note the undocumented fact that the __invoke magic method can take any number of arguments (or none).
Example:
<?php
class InvokeNoParams {
function __invoke()
{
print __METHOD__ . PHP_EOL;
$i = 1;
foreach (func_get_args() as $arg) {
print "The value of \$param{$i} is: " . $arg . PHP_EOL;
++$i;
}
print PHP_EOL;
}
}
class InvokeSingleParam {
function __invoke($param1)
{
print __METHOD__ . PHP_EOL;
print "Value of \$param1 is: " . $param1 . PHP_EOL . PHP_EOL;
}
}
class InvokeMultiParams {
function __invoke($param1, $param2, $param3) {
print __METHOD__ . PHP_EOL;
print "Value of \$param1 is: " . $param1 . PHP_EOL;
print "Value of \$param2 is: " . $param2 . PHP_EOL;
print "Value of \$param3 is: " . $param3 . PHP_EOL . PHP_EOL;
}
}
$no = new InvokeNoParams;
$single = new InvokeSingleParam;
$multi = new InvokeMultiParams;
$no(1, 2, 3);
$single('one param');
$multi('param 1', 'param 2', 'param 3');
?>
This outputs:
InvokeNoParams::__invoke
The value of $param1 is: 1
The value of $param2 is: 2
The value of $param3 is: 3
InvokeSingleParam::__invoke
Value of $param1 is: one param
InvokeMultiParams::__invoke
Value of $param1 is: param 1
Value of $param2 is: param 2
Value of $param3 is: param 3
rayRO ¶
8 years ago
If you use the Magical Method '__set()', be shure that the call of
<?php
$myobject->test['myarray'] = 'data';
?>
will not appear!
For that u have to do it the fine way if you want to use __set Method ;)
<?php
$myobject->test = array('myarray' => 'data');
?>
If a Variable is already set, the __set Magic Method already wont appear!
My first solution was to use a Caller Class.
With that, i ever knew which Module i currently use!
But who needs it... :]
There are quiet better solutions for this...
Here's the Code:
<?php
class Caller {
public $caller;
public $module;
function __call($funcname, $args = array()) {
$this->setModuleInformation();
if (is_object($this->caller) && function_exists('call_user_func_array'))
$return = call_user_func_array(array(&$this->caller, $funcname), $args);
else
trigger_error("Call to Function with call_user_func_array failed", E_USER_ERROR);
$this->unsetModuleInformation();
return $return;
}
function __construct($callerClassName = false, $callerModuleName = 'Webboard') {
if ($callerClassName == false)
trigger_error('No Classname', E_USER_ERROR);
$this->module = $callerModuleName;
if (class_exists($callerClassName))
$this->caller = new $callerClassName();
else
trigger_error('Class not exists: \''.$callerClassName.'\'', E_USER_ERROR);
if (is_object($this->caller))
{
$this->setModuleInformation();
if (method_exists($this->caller, '__init'))
$this->caller->__init();
$this->unsetModuleInformation();
}
else
trigger_error('Caller is no object!', E_USER_ERROR);
}
function __destruct() {
$this->setModuleInformation();
if (method_exists($this->caller, '__deinit'))
$this->caller->__deinit();
$this->unsetModuleInformation();
}
function __isset($isset) {
$this->setModuleInformation();
if (is_object($this->caller))
$return = isset($this->caller->{$isset});
else
trigger_error('Caller is no object!', E_USER_ERROR);
$this->unsetModuleInformation();
return $return;
}
function __unset($unset) {
$this->setModuleInformation();
if (is_object($this->caller)) {
if (isset($this->caller->{$unset}))
unset($this->caller->{$unset});
}
else
trigger_error('Caller is no object!', E_USER_ERROR);
$this->unsetModuleInformation();
}
function __set($set, $val) {
$this->setModuleInformation();
if (is_object($this->caller))
$this->caller->{$set} = $val;
else
trigger_error('Caller is no object!', E_USER_ERROR);
$this->unsetModuleInformation();
}
function __get($get) {
$this->setModuleInformation();
if (is_object($this->caller)) {
if (isset($this->caller->{$get}))
$return = $this->caller->{$get};
else
$return = false;
}
else
trigger_error('Caller is no object!', E_USER_ERROR);
$this->unsetModuleInformation();
return $return;
}
function setModuleInformation() {
$this->caller->module = $this->module;
}
function unsetModuleInformation() {
$this->caller->module = NULL;
}
}
// Well this can be a Config Class?
class Config {
public $module;
public $test;
function __construct()
{
print('Constructor will have no Module Information... Use __init() instead!<br />');
print('--> '.print_r($this->module, 1).' <--');
print('<br />');
print('<br />');
$this->test = '123';
}
function __init()
{
print('Using of __init()!<br />');
print('--> '.print_r($this->module, 1).' <--');
print('<br />');
print('<br />');
}
function testFunction($test = false)
{
if ($test != false)
$this->test = $test;
}
}
echo('<pre>');
$wow = new Caller('Config', 'Guestbook');
print_r($wow->test);
print('<br />');
print('<br />');
$wow->test = '456';
print_r($wow->test);
print('<br />');
print('<br />');
$wow->testFunction('789');
print_r($wow->test);
print('<br />');
print('<br />');
print_r($wow->module);
echo('</pre>');
?>
Outputs something Like:
Constructor will have no Module Information... Use __init() instead!
--> <--
Using of __init()!
--> Guestbook <--
123
456
789
Guestbook
ddavenport at newagedigital dot com ¶
10 years ago
One of the principles of OOP is encapsulation--the idea that an object should handle its own data and no others'. Asking base classes to take care of subclasses' data, esp considering that a class can't possibly know how many dozens of ways it will be extended, is irresponsible and dangerous.
Consider the following...
<?php
class SomeStupidStorageClass
{
public function getContents($pos, $len) { ...stuff... }
}
class CryptedStorageClass extends SomeStupidStorageClass
{
private $decrypted_block;
public function getContents($pos, $len) { ...decrypt... }
}
?>
If SomeStupidStorageClass decided to serialize its subclasses' data as well as its own, a portion of what was once an encrypted thingie could be stored, in the clear, wherever the thingie was stored. Obviously, CryptedStorageClass would never have chosen this...but it had to either know how to serialize its parent class's data without calling parent::_sleep(), or let the base class do what it wanted to.
Considering encapsulation again, no class should have to know how the parent handles its own private data. And it certainly shouldn't have to worry that users will find a way to break access controls in the name of convenience.
If a class wants both to have private/protected data and to survive serialization, it should have its own __sleep() method which asks the parent to report its own fields and then adds to the list if applicable. Like so....
<?php
class BetterClass
{
private $content;
public function __sleep()
{
return array('basedata1', 'basedata2');
}
public function getContents() { ...stuff... }
}
class BetterDerivedClass extends BetterClass
{
private $decrypted_block;
public function __sleep()
{
return parent::__sleep();
}
public function getContents() { ...decrypt... }
}
?>
The derived class has better control over its data, and we don't have to worry about something being stored that shouldn't be.
jon at webignition dot net ¶
6 years ago
The __toString() method is extremely useful for converting class attribute names and values into common string representations of data (of which there are many choices). I mention this as previous references to __toString() refer only to debugging uses.
I have previously used the __toString() method in the following ways:
- representing a data-holding object as:
- XML
- raw POST data
- a GET query string
- header name:value pairs
- representing a custom mail object as an actual email (headers then body, all correctly represented)
When creating a class, consider what possible standard string representations are available and, of those, which would be the most relevant with respect to the purpose of the class.
Being able to represent data-holding objects in standardised string forms makes it much easier for your internal representations of data to be shared in an interoperable way with other applications.
Dérico Filho ¶
8 years ago
Since PHP 5.2.0, you'll always get an error like this:
"Object of class foo could not be converted to string"
When one tries to use an object as string, for instance:
class Test{}
echo new Test();
Thus, one way to avoid this problem is to programme the magic method __toString.
However, in the older versions, it would output a string saying that it was an object together a unique obj id. Therefore, the __toString() method must comply with this behaviour.
My suggestion:
class Test{
function __toString(){
if(!isset($this->__uniqid))
$this->__uniqid = md5(uniqid(rand(), true));
return(get_class($this)."@".$this->__uniqid);
}
}
echo new Test();
would output something like this:
Test@6006ba04f5569544c10a588b04849cf7
michal dot kocarek at seznam dot cz ¶
6 years ago
Remember that setters and getters (__set, __get) will work in your class as long as you NOT SET the property with given name.
If you still want to have the public property definition in the class source code (phpDocumentor, editor code completition, or any other reason) when using these magic methods, simply unset() your public properties inside the constructor.
__set/__get function will be called and code reader will see at first sight, which public properties are available.
Example:
<?php
class user {
/**
* @var int Gets and sets the user ID
*/
public $UserID;
private $_userID;
public function __construct() {
// All the magic is in single line:
// We unset public property, so our setters and getters
// are used and phpDoc and editors with code completition are happy
unset($this->UserID);
}
public function __set($key, $value) {
// assign value for key UserID to _userID property
}
public function __get($key) {
// return value of _userID for UserID property
}
}
?>
jstubbs at work-at dot co dot jp ¶
8 years ago
$myclass->foo['bar'] = 'baz';
When overriding __get and __set, the above code can work (as expected) but it depends on your __get implementation rather than your __set. In fact, __set is never called with the above code. It appears that PHP (at least as of 5.1) uses a reference to whatever was returned by __get. To be more verbose, the above code is essentially identical to:
$tmp_array = &$myclass->foo;
$tmp_array['bar'] = 'baz';
unset($tmp_array);
Therefore, the above won't do anything if your __get implementation resembles this:
function __get($name) {
return array_key_exists($name, $this->values)
? $this->values[$name] : null;
}
You will actually need to set the value in __get and return that, as in the following code:
function __get($name) {
if (!array_key_exists($name, $this->values))
$this->values[$name] = null;
return $this->values[$name];
}
danillo dot paiva dot toledo at gmail dot com ¶
1 year ago
While I was studying Ruby I saw as such interesting things as properties created + its getters and setters in just one line.
I tryied to do the same in PHP and this is the code I have
class Father {
public function __call($name, $args) {
if(isset($this->$name)) {
if(isset($args[0]))
return $this->$name = $args[0];
return $this->$name;
}
return false;
}
}
class Child extends Father {
public $country = "Brazil";
public $state = "Sao Paulo";
}
Sometimes we don't need things like that on all classes but is quite interesting.
igorbt ¶
1 year ago
In recent versions of PHP, if you define __toString with arguments it will trigger a Fatal error: "__tostring() cannot take arguments". But, if you really need this (like I needed, because my framework heavily used these arguments), you have a workaround:
<?php
class a
{
public function __toString() {
list($a) = func_get_args();
return $a;
}
}
$a = new a();
echo $a->__toString('PHP'); // PHP
?>
osbertv at yahoo dot com ¶
3 years ago
Invoking a class inside a class results in an error.
<?php
class A
{
public function __invoke()
{
echo "Invoking A() Class";
}
}
class B
{
public $a;
public function __construct()
{
$this->a = new A();
}
public function __invoke()
{
echo "Invoking B() Class";
}
}
$a = new A();
$b = new B();
$a();
$b();
$b->a();
?>
returns
Invoking B() Class
PHP Fatal error: Call to undefined method B::a()
Anonymous ¶
4 years ago
C++-style operator overloading finally makes an appearance with the introduction to __invoke(). Unfortunately, with just '()'. In that sense, it is no more useful than having a default class method (probably quite useful actually) and not having to type out an entire method name. Complimenting wbcarts at juno dot com's point class below, the following allows calculating distance between one or more graph points...
<?php
class point {
public $x;
public $y;
function __construct($x=0, $y=0) {
$this->x = (int) $x;
$this->y = (int) $y;
}
function __invoke() {
$args = func_get_args();
$total_distance = 0;
$current_loc = $this;
foreach ($args as $arg) {
if (is_object($arg) and (get_class($arg) === get_class($this))) {
$total_distance += sqrt(pow($arg->x - $current_loc->x, 2) + pow((int) $arg->y - $current_loc->y, 2));
$current_loc = $arg;
}
else {
trigger_error("Arguments must be objects of this class.");
return;
}
}
return $total_distance;
}
}
$p1 = new point(1,1);
$p2 = new point(23,-6);
$p3 = new point(15,20);
echo $p1($p2,$p3,$p1); // round trip 73.89
?>
Functionally, __invoke() can also be used to mimic the use of variable functions. Sadly, attempting any calling of __invoke() on a static level will produce a fatal error.
wbcarts at juno dot com ¶
6 years ago
To be helpful, the __toString() method should return the class name and the state of all its properties inside square brackets.
<?php
class Point {
protected $x, $y;
public function __construct($xVal = 0, $yVal = 0) {
$this->x = $xVal;
$this->y = $yVal;
}
public function __toString() { // the function we're interested in...
return "Point[x=$this->x, y=$this->y]";
}
}
$point1 = new Point(10, 10);
$point2 = new Point(50, 50);
echo $point1 . '<br>';
echo $point2 . '<br><br>';
?>
Point[x=10, y=10]
Point[x=50, y=50]
Classes that include objects, should call that objects __toString() method.
<?php
class Line {
protected $start, $end;
public function __construct(Point $p1, Point $p2){
$this->start = $p1;
$this->end = $p2;
}
public function __toString() { // the function we're interested in...
return 'Line[start=' . $this->start->__toString() . // call __toString()
', end=' . $this->end->__toString() . ']'; // call __toString()
}
}
echo (new Line($point1, $point2));
?>
Line[start=Point[x=10, y=10], end=Point[x=50, y=50]]
Anonymous ¶
6 years ago
Serializing objects is problematic with references. This is solved redefining the __sleep() magic method. This is also problematic when parent class has private variables since the parent object is not accessible nor its private variables from within the child object.
I found a solution that seems working for classes that implements this __sleep() method, and for its subclasses. Without more work in subclasses. The inheritance system does the trick.
Recursively __sleep() call parent' __sleep() and return the whole array of variables of the object instance to be serialized.
<?php
class foo {
}
class a {
private $var1;
function __construct(foo &$obj = NULL) {
$this->var1 = &$obj;
}
/** Return its variables array, if its parent exists and the __sleep method is accessible, call it and push the result into the array and return the whole thing. */
public function __sleep() {
$a = array_keys(get_object_vars(&$this));
if (method_exists(parent, '__sleep')) {
$p = parent::__sleep();
array_push($a, $p);
};
return $a;
}
}
class b extends a {
function __construct(foo &$obj = NULL) {
parent::__construct($obj);
}
}
session_start();
$myfoo = &new foo();
$myb = &new b($myfoo);
$myb = unserialize(serialize(&$myb));
?>
This should work, I haven't tested deeper.
Travis Swicegood ¶
7 years ago
There is no need to use eval() to mimic mixins (i.e., multiple inheritance) within PHP 5. You only need to:
<?php
class MyClass
{
private $_obj = null;
public function __construct($obj)
{
$this->_obj = $obj;
}
public function __call($method, $args)
{
if (!method_exists($this->_obj, $method)) {
throw new Exception("unknown method [$method]");
}
return call_user_func_array(
array($this->_obj, $method),
$args
);
}
}
?>
You could just as easily add an addMixin() method that would allow you to add multiple objects to an array, and then iterate over that array until you found the right method. As noted, these are referred to as a Mixins in other languages.
taylorbarstow at google's mail service ¶
8 years ago
I've just come accross something interesting relating to storing PHP5 objects in a session. If you don't provide an __autoload(), then you MUST load the class definition before calling session_start(). I guess that when you call session_start(), any objects in the session are unserialized then and there and placed into $_SESSION. If you don't provide the class definition before calling session_start(), your object will get the class __PHP_Incomplete_Class, and you won't be able to use it for anything.
Examples:
<?php
session_start();
require_once 'MyClass.php';
$obj = new MyClass;
$_SESSION['obj'] = $obj;
?>
Works fine. Then on a subsequent page load:
<?php
session_start();
require_once 'MyClass.php';
$_SESSION['obj']->callSomeMethod();
?>
Fatal error: The script tried to execute a method or access a property of an incomplete object. Please ensure that the class definition "MyClass" of the object you are trying to operate on was loaded _before_ unserialize() gets called or provide a __autoload() function to load the class definition.
But if you do this instead, it works fine:
<?php
require_once 'MyClass.php';
session_start();
$_SESSION['obj']->callSomeMethod();
?>
Hopefully in some future release of PHP, __PHP_Incomplete_Class will be smart enough to check for a class definition at time of use (method call or property operation), and, if the class exists, magically "complete" itself and turn into the desired object.
b dot schoppmeier at bas-consult dot de ¶
9 years ago
The sequence of events regarding __sleep and __destruct is unusual __ as __destruct is called before __sleep. The following code snippet:
<?php
$sequence = 0;
class foo {
public $stuff;
public function __construct($param) {
global $sequence;
echo "Seq: ", $sequence++, " - constructor\n";
$this->stuff = $param;
}
public function __destruct() {
global $sequence;
echo "Seq: ", $sequence++, " - destructor\n";
}
public function __sleep() {
global $sequence;
echo "Seq: ", $sequence++, " - __sleep\n";
return array("stuff");
}
public function __wakeup() {
global $sequence;
echo "Seq: ", $sequence++, " - __wakeup\n";
}
}
session_start();
$_SESSION["obj"] = new foo("A foo");
?>
yields the output:
Seq: 0 - constructor
Seq: 1 - destructor
Seq: 2 - __sleep
Only when you end your script with a call to session_write_close() as in:
<?php
$sequence = 0;
class foo {
public $stuff;
public function __construct($param) {
global $sequence;
echo "Seq: ", $sequence++, " - constructor\n";
$this->stuff = $param;
}
public function __destruct() {
global $sequence;
echo "Seq: ", $sequence++, " - destructor\n";
}
public function __sleep() {
global $sequence;
echo "Seq: ", $sequence++, " - __sleep\n";
return array("stuff");
}
public function __wakeup() {
global $sequence;
echo "Seq: ", $sequence++, " - __wakeup\n";
}
}
session_start();
$_SESSION["obj"] = new foo("A foo");
session_write_close();
?>
the sequence is as common sense would expect it to be as the following output shows:
Seq: 0 - constructor
Seq: 1 - __sleep
Seq: 2 - destructor
docey ¶
9 years ago
about __sleep and _wakeup, consider using a method like this:
class core
{
var $sub_core; //ref of subcore
var $_sleep_subcore; // place where serialize version of sub_core will be stored
function core(){
$this->sub_core = new sub_core();
return true;
}
function __wakeup()
{
// on wakeup of core, core unserializes sub_core
// wich it had stored when it was serialized itself
$this->sub_core = unserialize($this->_sleep_subcore);
return true;
}
function __sleep()
{
// sub_core will be serialized when core is serialized.
// the serialized subcore will be stored as a string inside core.
$this->_sleep_subcore = serialize($this->sub_core);
$return_arr[] = "_sleep_subcore";
return $return_arr;
}
}
class sub_core
{
var $info;
function sub_core()
{
$this->info["somedata"] = "somedata overhere"
}
function __wakeup()
{
return true;
}
function __sleep()
{
$return_arr[] = "info"
return $return_arr;
}
}
this way subcore is being serialized by core when core is being serialized. subcore handles its own data and core stores it as a serialize string inside itself. on wakeup core unserializes subcore.
this may have a performance cost, but if you have many objects connected this way this is the best way of serializing them. you only need to serialize the the main object wich will serialize all those below which will serialize all those below them again. in effect causing a sort of chainreaction in wich each object takes care of its own info.
offcoarse you always need to store the eventualy serialized string in a safe place. somebody got experience with this way of __wakeup and __sleep.
works in PHP4&5
martin dot goldinger at netserver dot ch ¶
9 years ago
When you use sessions, its very important to keep the sessiondata small, due to low performance with unserialize. Every class shoud extend from this class. The result will be, that no null Values are written to the sessiondata. It will increase performance.
<?
class BaseObject
{
function __sleep()
{
$vars = (array)$this;
foreach ($vars as $key => $val)
{
if (is_null($val))
{
unset($vars[$key]);
}
}
return array_keys($vars);
}
};
?>
Wesley ¶
3 years ago
Warning __toString can be triggerd more then one time
<?php
if(strstr(substr($obj,0,1024), 'somestuff')
echo $obj;
return 'missing somestuff at the start, create container!';
substr() will trigger a __toString aswell as echo $obj;
?>
wich cause a performance issue since it will gather all data twice.
what i used as a hotfix:
<?php
__toString(){
if(null === $this->sToString)
$this->sToString = $this->_show();
return $this->sToString;
}
?>
rudie-de-hotblocks at osu1 dot php dot net ¶
5 years ago
Note also that the constructor is executed also, and before __set_state(), making this magic function less magic, imho, (except for the ability to assign private members).
patricknegri at gmail dot com ¶
6 years ago
Imports Pattern - Extend Classes in Real Time:
<?php
class BaseClass
{
var $__imported;
var $__imported_functions;
function __construct()
{
$__imported = Array();
$__imported_functions = Array();
}
function Imports($object)
{
$new_imports = new $object();
$imports_name = get_class($new_imports);
array_push( $__imported, Array($imports_name,$new_imports) );
$imports_function = get_class_methods($new_imports);
foreach ($imports_function as $i=>$function_name)
{
$this->__imported_functions[$function_name] = &$new_imports;
}
}
function __call($m, $a)
{
if (array_key_exists($m,$this->__imported_functions))
{
return call_user_func_array(Array($this->__imported_functions[$m],$m),$a);
}
throw new ErrorException ('Call to Undefined Method/Class Function', 0, E_ERROR);
}
}
class ExternalFunc
{
function TestB()
{
echo "External Imported!";
}
}
class B extends BaseClass
{
function __construct()
{
$this->Imports("ExternalFunc");
}
function Msg()
{
echo "Hello world<br />";
}
}
$b = new B();
$b->Msg();
// or call $b->Imports("ExternalFunc");
$b->TestB();
//$b->TestB(1,3,4);
?>
yanleech at gmail dot com ¶
6 years ago
Maybe we can using unserialize() & __wakeup() instead "new" when creating a new instance of class.
Consider following codes:
class foo
{
static public $WAKEUP_STR = 'O:3:"foo":0:{}';
public function foo(){}
public function bar(){}
}
$foo = unserialize(foo::$WAKEUP_STR);
adar at darkpoetry dot de ¶
7 years ago
Maybe not really new and all in all definitely not the best solution,but if you cant extend a class (if your class alreay extends an abstract or other things like that) you can 'fake' a extend.
<?php
class MyClass
extends SomeAbstractUnknownClass {
private $classObject;
public function __construct ( classObject $classToExtend ) {
$this->classObject = $classToExtend;
}
public function __call($func, $var) {
if ( !count($var) ) {
return $this->classObject->$func($var);
} else {
$str = '';
$values = array_values($var);
for ( $i=0; $i<count($values); $i++ ) {
$str .= "'".$values[$i]."' ,";
}
$str = substr($str, 0, -2);
return eval('return $this->classObject->'.$func.'('.$str.');');
}
}
}
?>
So if you'll do a $myClass->unknownMethod() and it is found neither in MyClass nor in SomeAbstractUnknownClass, MyClass will try to call this method in $classObject.
I use this for 'extending' a UserObject-Class which already extends an other one.
Better solutions are always welcome ;)
jeffxlevy at gmail dot com ¶
9 years ago
Intriguing what happens when __sleep() and __wakeup() and sessions() are mixed. I had a hunch that, as session data is serialized, __sleep would be called when an object, or whatever, is stored in _SESSION. true. The same hunch applied when session_start() was called. Would __wakeup() be called? True. Very helpful, specifically as I'm building massive objects (well, lots of simple objects stored in sessions), and need lots of automated tasks (potentially) reloaded at "wakeup" time. (for instance, restarting a database session/connection).
mastabog at hotmail dot com ¶
9 years ago
In reply to krisj1010 at gmail.com below:
__sleep() handles protected/private properties very well. You should never rely on get_class_vars() to retrieve property names since this function only returns the public properties. Use the Reflection API instead for that purpose. Better yet, if you know which ones you want to save it is always faster to specify the return array manually.
Anonymous ¶
4 years ago
Concerning __set() with protected/private/overloaded properties, the behavior might not be so intuitive without knowing some underlying rules. Consider this test object for the following examples...
<?php
class A {
protected $test_int = 2;
protected $test_array = array('key' => 'test');
protected $test_obj;
function __construct() {
$this->test_obj = new stdClass();
}
function __get($prop) {
return $this->$prop;
}
function __set($prop, $val) {
$this->$prop = $val;
}
}
$a = new A();
?>
Combined Operators (.=, +=, *=, etc): you must also define a companion __get() method to grant write -and- read access to the property. Remember, "$x += $y" is shorthand for "$x = $x + $y". In other words, "__set($x, (__get($x) + $y))".
Properties that are Arrays: attempting to set array values like "$a->test_array[] = 'asdf';" from outside this object will result in an "Indirect modification of overloaded property" notice and the operation completely ignored. You can't use '[]' for array value assignment in this context (with the exception only if you made __get() return by reference, in which case, it would work fine and bypass the __set() method altogether). You can work around this doing something like unioning the array instead:
<?php
$a->test_array[] = 'asdf'; // notice given and ignored unless __get() was declared to return by reference
$a->test_array += array(1 => 'asdf'); // to add a key/value
$a->test_array = array("key" => 'asdf') + $a->test_array; // to overwrite a key/value.
?>
Properties that are Objects: as long as you have that __get() method, you can freely access and alter that sub object's own properties, bypassing __set() entirely. Remember, objects are assigned and passed by reference naturally.
<?php
$a->test_obj->prop = 1; // fine if $a did not have a set method declared.
?>
All above tested in 5.3.2.
alejandro dot gama at gmail dot com ¶
7 years ago
Referering my previus note: there was an error in the code. But i find a better way:
<?
session_start();
class Classes{
private $name;
private $statics;
function __construct($name){
$this->name=$name;
$this->statics=array();
}
function setStatic($k,$v){
if(!is_resource($v))
$this->statics[$k]=$v;
}
function __wakeup(){
foreach($this->statics as $k=>$v)
eval($this->name."::\$".$k."=\$this->statics['".$k."'];");
}
}
function storeStaticAttributes(){
$classes=get_declared_classes();
foreach($classes as $name){
$reflect=new ReflectionClass($name);
if($reflect->isUserDefined()){
$statics=$reflect->getStaticProperties();
if(empty($_SESSION["_classes"]))
$_SESSION["_classes"]=array();
if(empty($_SESSION["_classes"][$name]))
$_SESSION["_classes"][$name]=new Classes($name);
foreach($statics as $k=>$v)
$_SESSION["_classes"][$name]->setStatic($k,$v);
}
}
}
register_shutdown_function('storeStaticAttributes');
?>
ksamvel at gmail dot com ¶
8 years ago
To copy base part of derived class appropriate method in base should be defined. E.g.:
class A {
public function setAVar( $oAVar) { $this->oAVar = $oAVar; }
public function getAVar() { return $this->oAVar; }
public function copyA( &$roDest) {
if( $roDest instanceof A)
$this->oAVar = $roDest->oAVar;
}
private $oAVar;
}
class B extends A {
public function setBVar( $oBVar) { $this->oBVar = $oBVar; }
public function getBVar() { return $this->oBVar; }
private $oBVar;
}
$oA = new A();
$oB = new B();
$oA->setAVar( 4);
$oB->setAVar( 5);
$oB->setBVar( 6);
echo "oA::oAVar " . $oA->getAVar() . "<br>";
echo "oB::oAVar " . $oB->getAVar() . "<br>";
echo "oB::oBVar " . $oB->getBVar() . "<br>";
echo "<br>";
$oB->copyA( $oA);
echo "oA::oAVar " . $oA->getAVar() . "<br>";
echo "oB::oAVar " . $oB->getAVar() . "<br>";
echo "oB::oBVar " . $oB->getBVar() . "<br>";
Output:
oA::oAVar 4
oB::oAVar 5
oB::oBVar 6
oA::oAVar 4
oB::oAVar 4
oB::oBVar 6
moechofe ¶
5 years ago
__invoke() cannot be used to create fluente interface like in the "D language"
<?php
class CallableClass
{
var $next;
function __invoke($x)
{
var_dump($x);
return $this;
}
}
$obj = new CallableClass;
$obj->next = new CallableClass;
var_dump( $obj(5) ); // OK!
var_dump( $obj(5)(6) ); // Parse error
var_dump( $obj->next(7) ); // Fatal error: Call to undefined method CallableClass::next()
var_dump( {$obj->next}(7) ); // Parse error
?>
qfox at ya dot ru ¶
2 years ago
For those of you who have the same trouble as osbertv.
<?php
// ...
$a = new A();
$b = new B();
$a();
$b();
$b->a();
?>
PHP Fatal error: Call to undefined method B::a()
It's because PHP have bug in parsing syntax (a lot of).
Just make it easier to parse and it would work.
For example, like this:
<?php
$c = $b->a;
$c();
?>
Or this, if you use 5.4 (if you using 5.3 just move call function to the each class which need it or to some base abstract class):
<?php
trait TInnerClosuresInvoker {
function __call($method, $args) {
if (isset($this->$method) && is_callable($method)) {
$closure = $this->$method;
call_user_func_array($closure, $args);
} else {
trigger_error('Call to undefined method '.__CLASS__.'::'.$method.'()', E_USER_ERROR);
}
}
}
class A {
use TInnerClosuresInvoker;
...
}
?>
It's a little bit dirty, but it works.
tom ¶
4 years ago
Note a common pitfall when using __wakeup.
If you unserialize a datastructure, you may not rely on the parent object to have been fully unserialized by the time __wakeup is called. Example
<?php
class A {
public $b;
public $name;
}
class B extends A {
public $parent;
public function __wakeup() {
var_dump($parent->name);
}
}
$a = new A();
$a->name = "foo";
$a->b = new B();
$a->b->parent = $a;
$s = serialize($a);
$a = unserialize($s);
?>
Expected output: "foo".
Actual output: NULL.
Reason: $b is unserialized before $name. By the time B::__wakeup is called, $a->name does not yet have a value.
So be aware that the order in which your class variables are defined is important! You need to manually order them by dependencies - or write a __sleep function and order them by depencies there. (Currently I can't tell which option I hate more)
zach at bygeekz dot com ¶
5 years ago
Try this one on.
<?php
$ret = new Test(true);
var_dump((bool)(string)$ret);
var_dump($ret);
$ret=null;
$ret = new Test();
var_dump((bool)(string)$ret);
var_dump($ret);
class Test {
protected $state=null;
function __construct($state=null) {
$this->state = $state;
}
function __toString() {
if ($this->state) { return "1"; } else { return "0"; }
}
}
?>
You could for instance do..
if(!(bool)(string)$ret) { do_something!; }
Alternatively, just make state public, and check it.
if(!$ret->state) {}.
There is no automatic way I have found aside from some internal state check to verify a class. It will always return an object. The only way around that is to force it out to string either where I did, or $ret = (string) new Test(); then test the bool of your output..
if (!$ret) { echo "noooo!"; }
But now you have no calling methods, so I hope you passed some data in to get a usable string out.
Of course, if your class isn't named test, you can add a method..
public function test() {
return $this->state;
}
Logically that will work regardless of the _toString(), but I had hoped to post this to help others see that there are a multitude of ways to check the validity of a class once it is loaded. In __construct you can add any number of checks and set your state appropriately.
muratyaman at gmail dot com ¶
6 years ago
Regarding __toString:
<?php
class my_tag_A{
public $id='';
public $href='';
public $target='';
public $class='';
public $label='';
function __construct($href, $label){
$this->href = $href;
$this->label = $label;
}
public function __toString(){
return '<a '.$this->nz_arr(array('id', 'href', 'target', 'class')). ' >' . $this->label . '</a>';
}
function nz_arr($attrib_arr){
$s = '';
foreach($attrib_arr as $attrib){
$s .= $this->nz($attrib);
}
return $s;
}
/**
* Print the tag attribute if it is not blank, such as id="$this->id"
* @param string $attrib
* @return string
*/
function nz($attrib){
$s = '';
if($this->$attrib != '') $s = $attrib .' = "' . $this->$attrib . '"';
return $s;
}
//This causes RECURSION because of parsing between double quotes. This is a very UNEXPECTED behaviour!
function nz_($attrib){
$s = '';
if($this->$attrib != '') $s = "$attrib = \"$this->$attrib\"";
return $s;
}
}//end class
//usage
$a = new my_tag_A('abc.php', 'ABC'); $a->target = '_blank';
echo $a;
//prints:
// <a href="abc.php" target="_blank" >ABC</a>
?>
rc @ nospam @ vorklift dot sea oh em ¶
6 years ago
A note: __wakeup occurs before saving the unserialization of an session object.
Therefore, $_SESSION['var']::__wakeup() setting $_SESSION['var'] = new Class() will fail and $_SESSION['var'] will remain unchanged.
This means that if you have a pseudo-temporary object that contains a class to auto revert to, you have to revert that session object in the initialization of the website rather than via a __wakeup() script.
Voitcus at wp dot pl ¶
2 years ago
You don't need to serialize the class default values, only those which have changed. It might be important for large objects. Note the example below, for simplicity, always serializes arrays and objects.
<?php
class MyBaseClass {
public $name='object'; // these are default class values
public $test=1;
public $test2; // equals to NULL in fact
public function __construct(){
$this->test2='some text'; // this is not a default value, although called in the constructor
}
public function __sleep(){
// default class values:
$defaults=get_class_vars(get_class($this)); // not __CLASS__ or self::, if you'd like to use in descendant classes
// values of $this object:
$present=get_object_vars($this);
$result=array(); // output array
foreach($present as $key=>$value){
if(!is_resource($defaults[$key]) && ( // don't store resources
is_object($defaults[$key]) || // always store objects
is_array($defaults[$key]) || // and arrays
$defaults[$key]!==$value) // and of course all that is not the default value
) // tip: try is_scalar as well
$result[]=$key;
}
return $result;
}
}
$obj1=new MyBaseClass();
echo ($s1=serialize($obj1))."<br>"; // only test2 is stored, as it was changed in the constructor
$obj2=new MyBaseClass();
$obj2->name='object 2'; // change default value here
echo ($s2=serialize($obj2))."<br>"; // stored name and test2
$obj3=new MyBaseClass();
$obj3->test2=NULL; // switch back to default value
echo ($s3=serialize($obj3))."<br>"; // nothing is stored but the class name
// let us check if we can retrieve the objects
unset($obj1, $obj2, $obj3);
$obj1=unserialize($s1);
$obj2=unserialize($s2);
$obj3=unserialize($s3);
var_dump($obj1);
var_dump($obj2);
var_dump($obj3);
?>
