Valori restituiti
If you want to call a static function (PHP5) in a variable method:
Make an array of two entries where the 0th entry is the name of the class to be invoked ('self' and 'parent' work as well) and the 1st entry is the name of the function. Basically, a 'callback' variable is either a string (the name of the function) or an array (0 => 'className', 1 => 'functionName').
Then, to call that function, you can use either call_user_func() or call_user_func_array(). Examples:
<?php
class A {
protected $a;
protected $c;
function __construct() {
$this->a = array('self', 'a');
$this->c = array('self', 'c');
}
static function a($name, &$value) {
echo $name,' => ',$value++,"\n";
}
function b($name, &$value) {
call_user_func_array($this->a, array($name, &$value));
}
static function c($str) {
echo $str,"\n";
}
function d() {
call_user_func_array($this->c, func_get_args());
}
function e() {
call_user_func($this->c, func_get_arg(0));
}
}
class B extends A {
function __construct() {
$this->a = array('parent', 'a');
$this->c = array('self', 'c');
}
static function c() {
print_r(func_get_args());
}
function d() {
call_user_func_array($this->c, func_get_args());
}
function e() {
call_user_func($this->c, func_get_args());
}
}
$a =& new A;
$b =& new B;
$i = 0;
A::a('index', $i);
$a->b('index', $i);
$a->c('string');
$a->d('string');
$a->e('string');
# etc.
?>
Funzioni variabili
PHP supporta il concetto di funzioni variabili. Ciò significa che se un nome di variabile ha le parentesi accodate ad esso, PHP cercherà una funzione con lo stesso nome del valore della variabile, e cercherà di eseguirla. Tra le altre cose, ciò puo essere usato per implementare delle callbacks, tabelle di funzioni e così via.
Le funzioni variabili non funzionano con costrutti di linguaggio come echo, print, unset(), isset(), empty(), include, require e simili. Occorre costruire una propria funzione per utilizzare questi costrutti come variabili per funzioni.
Example #1 Esempio di funzioni variabili
<?php
function foo() {
echo "In foo()<br />\n";
}
function bar($arg = '')
{
echo "In bar(); l'argomento era '$arg'.<br />\n";
}
// Questa è la funzione per usare echo
function echoit($string)
{
echo $string;
}
$func = 'foo';
$func(); // questa chiama foo()
$func = 'bar';
$func('test'); // questa chiama bar()
$func = 'echoit';
$func('test'); // questa chiama echoit()
?>
Tramite le funzioni variabili si possono eseguire anche metodi di oggetti.
Example #2 Esempio di un metodo variabile
<?php
class Foo
{
function Variable()
{
$name = 'Bar';
$this->$name(); // Questo esegue il metodo Bar()
}
function Bar()
{
echo "This is Bar";
}
}
$foo = new Foo();
$funcname = "Variable";
$foo->$funcname(); // Questo esegue $foo->Variable()
?>
Quando si chiamano dei metodi statici, la chiamata a funzione ha la precedenza sull'operatore di proprietà statica:
Example #3 Esempio di metodo variabile con proprietà statiche
<?php
class Foo
{
static $variable = 'static property';
static function Variable()
{
echo 'Method Variable called';
}
}
echo Foo::$variable; // Questo stampa 'static property'. Non ha bisogno di una $variable in questo ambito.
$variable = "Variable";
Foo::$variable(); // Questo chiama $foo->Variable() leggendo $variable da questo ambito.
?>
Vedere anche is_callable(), call_user_func(), variabili variabili e function_exists().
add a note
User Contributed Notes
Funzioni variabili - [11 notes]
boards at gmail dot com ¶
7 years ago
ian at NO_SPAM dot verteron dot net ¶
10 years ago
A good method to pass around variables containing function names within some class is to use the same method as the developers use in preg_replace_callback - with arrays containing an instance of the class and the function name itself.
function call_within_an_object($fun)
{
if(is_array($fun))
{
/* call a function within an object */
$fun[0]->{$fun[1]}();
}
else
{
/* call some other function */
$fun();
}
}
function some_other_fun()
{
/* code */
}
class x
{
function fun($value)
{
/* some code */
}
}
$x = new x();
/* the following line calls $x->fun() */
call_within_an_object(Array($x, 'fun'));
/* the following line calls some_other_fun() */
call_within_an_object('some_other_fun');
anpatel at NOSPAM_cbu dot edu ¶
11 years ago
Yes interpolation can be very tricky. I suggest that you always use parenthesis, or curly brackets(whichever applies) to make your expression clear.
Dont ever depend on a language's expression parse preference order.
imurnane at internode on net ¶
2 years ago
Create and call a dynamically named function
<?php
$tmp = "foo";
$$tmp = function() {
global $tmp;
echo $tmp;
};
$$tmp();
?>
Outputs "foo"
madeinlisboa at yahoo dot com ¶
10 years ago
Finally, a very easy way to call a variable method in a class:
Example of a class:
class Print() {
var $mPrintFunction;
function Print($where_to) {
$this->mPrintFunction = "PrintTo$where_to";
}
function PrintToScreen($content) {
echo $content;
}
function PrintToFile($content) {
fputs ($file, $contents);
}
.. .. ..
// first, function name is parsed, then function is called
$this->{$this->mPrintFunction}("something to print");
}
AnonymousPoster at disposeamail dot com ¶
3 years ago
Variable functions allows higher-order programming.
Here is the classical map example.
<?php
/*
* Map function. At each $element of the $list, calls $fun([$arg1,[$arg2,[...,]],$element,$accumulator),
* stores the return value into $accumulator for the next loop. Returns the last return value of the function,
*
* Notes : uses call_user_func_array() so passing parameters doesn't depend on $fun signature
* It also returns FALSE upon error.
* Please check the php documentation for more information
*/
function map($fun, $list,$params=array()){
$acc=NULL;
$last=array_push($params, NULL,$acc)-1; // alloc $element and $acc at the end
foreach($list as $params[$last-1]){
$params[$last]=call_user_func_array($fun , $params );
}
$acc=array_pop($params);
return $acc;
}
function add($element,$acc){ // maybe only with multi-length function
if ($acc == NULL);
return $acc=$element+$acc;
}
$result=0;
$result=addTo($result,1);
$result=addTo($result,2);
$result=addTo($result,3);
echo "result = $result\n";
$result=0;
$result=map('addTo',array(1,2,3));
echo "result= $result\n";
?>
msmith at pmcc dot com ¶
11 years ago
Try the call_user_func() function. I find it's a bit simpler to implement, and at very least makes your code a bit more readable... much more readable and simpler to research for someone who isn't familiar with this construct.
Storm ¶
8 years ago
This can quite useful for a dynamic database class:
(Note: This just a simplified section)
<?php
class db {
private $host = 'localhost';
private $user = 'username';
private $pass = 'password';
private $type = 'mysqli';
public $lid = 0;
// Connection function
function connect() {
$connect = $this->type.'_connect';
if (!$this->lid = $connect($this->host, $this->user, $this->pass)) {
die('Unable to connect.');
}
}
}
$db = new db;
$db->connect();
?>
Much easier than having multiple database classes or even extending a base class.
Anonymous ¶
1 year ago
$ wget http://www.php.net/get/php_manual_en.tar.gz/from/a/mirror
$ grep -l "\$\.\.\." php-chunked-xhtml/function.*.html
List of functions that accept variable arguments.
<?php
array_diff_assoc()
array_diff_key()
array_diff_uassoc()
array()
array_intersect_ukey()
array_map()
array_merge()
array_merge_recursive()
array_multisort()
array_push()
array_replace()
array_replace_recursive()
array_unshift()
call_user_func()
call_user_method()
compact()
dba_open()
dba_popen()
echo()
forward_static_call()
fprintf()
fscanf()
httprequestpool_construct()
ibase_execute()
ibase_set_event_handler()
ibase_wait_event()
isset()
list()
maxdb_stmt_bind_param()
maxdb_stmt_bind_result()
mb_convert_variables()
newt_checkbox_tree_add_item()
newt_grid_h_close_stacked()
newt_grid_h_stacked()
newt_grid_v_close_stacked()
newt_grid_v_stacked()
newt_win_choice()
newt_win_entries()
newt_win_menu()
newt_win_message()
newt_win_ternary()
pack()
printf()
register_shutdown_function()
register_tick_function()
session_register()
setlocale()
sprintf()
sscanf()
unset()
var_dump()
w32api_deftype()
w32api_init_dtype()
w32api_invoke_function()
wddx_add_vars()
wddx_serialize_vars()
?>
michalmojz at gmail dot com ¶
2 years ago
You can make dynamic functions as well.
For example
<?php
$myFunction = function() {
echo 1;
};
if(is_callable($myFunction)) {
$myFunction();
}
?>
retro at enx dot org ¶
11 years ago
Another way to have php parse a variable within an object as a function is to simply set a temporary variable to its value. For example:
$obj->myfunction = "foo";
$x = $obj->myfunction;
$x(); // calls the function named "foo"