As previously noted exception linking was recently added (and what a god-send it is, it certainly makes layer abstraction (and, by association, exception tracking) easier).
Since <5.3 was lacking this useful feature I took some initiative and creating a custom exception class that all of my exceptions inherit from:
<?php
class SystemException extends Exception
{
private $previous;
public function __construct($message, $code = 0, Exception $previous = null)
{
parent::__construct($message, $code);
if (!is_null($previous))
{
$this -> previous = $previous;
}
}
public function getPrevious()
{
return $this -> previous;
}
}
?>
Hope you find it useful.
예외 확장하기
내장 Exception 클래스를 확장하여 사용자 정의 예외 클래스를 정의할 수 있습니다. 내장 Exception 클래스를 상속한 자식 클래스에서 다음 멤버와 프로퍼티에 접근할 수 있습니다.
Example #1 내장 Exception 클래스
<?php
class Exception
{
protected $message = 'Unknown exception'; // 예외 메시지
private $string; // __toString 캐시
protected $code = 0; // 사용자 정의 예외 코드
protected $file; // 예외가 발생한 소스 파일 이름
protected $line; // 예외가 발생한 소스 라인
private $trace; // backtrace
private $previous; // 중첩 예외의 경우 이전 예외
public function __construct($message = null, $code = 0, Exception $previous = null);
final private function __clone(); // 예외의 복제를 금지합니다.
final public function getMessage(); // 예외 메시지
final public function getCode(); // 예외 코드
final public function getFile(); // 소스 파일 이름
final public function getLine(); // 소스 라인
final public function getTrace(); // backtrace() 배열
final public function getPrevious(); // 이전 예외
final public function getTraceAsString(); // trace의 형식화 문자열
// Overrideable
public function __toString(); // 출력을 위한 형식화 문자열
}
?>
클래스가 내장 Exception 클래스를 상속받아 생성자를 재정의 할 경우에는, parent::__construct()를 호출하여 모든 사용가능한 데이터가 적합하게 할당될 수 있도록 하길 권합니다. __toString() 메쏘드를 덮어써서, 객체가 문자열로 표현될 때 사용자 출력을 제공할 수 있습니다.
Note:
예외는 복제할 수 없습니다. 예외에 대하여 clone을 하려 경우 치명적인
E_ERROR오류가 발생합니다.
Example #2 Exception 클래스 확장하기 (PHP 5.3.0+)
<?php
/**
* 사용자 예외 클래스 정의하기
*/
class MyException extends Exception
{
// 예외를 재정의해서 메시지를 필수값으로 만듭니다
public function __construct($message, $code = 0, Exception $previous = null) {
// 처리할 코드
// 모든 값이 할당되도록 합니다
parent::__construct($message, $code, $previous);
}
// 객체의 사용자 문자열 표현
public function __toString() {
return __CLASS__ . ": [{$this->code}]: {$this->message}\n";
}
public function customFunction() {
echo "A custom function for this type of exception\n";
}
}
/**
* 예외를 테스트할 클래스를 작성합니다
*/
class TestException
{
public $var;
const THROW_NONE = 0;
const THROW_CUSTOM = 1;
const THROW_DEFAULT = 2;
function __construct($avalue = self::THROW_NONE) {
switch ($avalue) {
case self::THROW_CUSTOM:
// throw custom exception
throw new MyException('1 is an invalid parameter', 5);
break;
case self::THROW_DEFAULT:
// throw default one.
throw new Exception('2 is not allowed as a parameter', 6);
break;
default:
// No exception, object will be created.
$this->var = $avalue;
break;
}
}
}
// 예제 1
try {
$o = new TestException(TestException::THROW_CUSTOM);
} catch (MyException $e) { // Will be caught
echo "Caught my exception\n", $e;
$e->customFunction();
} catch (Exception $e) { // Skipped
echo "Caught Default Exception\n", $e;
}
// 계속 실행
var_dump($o); // Null
echo "\n\n";
// 예제 2
try {
$o = new TestException(TestException::THROW_DEFAULT);
} catch (MyException $e) { // Doesn't match this type
echo "Caught my exception\n", $e;
$e->customFunction();
} catch (Exception $e) { // Will be caught
echo "Caught Default Exception\n", $e;
}
// 계속 실행
var_dump($o); // Null
echo "\n\n";
// 예제 3
try {
$o = new TestException(TestException::THROW_CUSTOM);
} catch (Exception $e) { // Will be caught
echo "Default Exception caught\n", $e;
}
// 계속 실행
var_dump($o); // Null
echo "\n\n";
// 예제 4
try {
$o = new TestException();
} catch (Exception $e) { // Skipped, no exception
echo "Default Exception caught\n", $e;
}
// 계속 실행
var_dump($o); // TestException
echo "\n\n";
?>
Note:
PHP 5.3.0 미만의 PHP 5 버전에서는 예외 중첩을 지원하지 않습니다. 이 예제를 실행하기 위해서 MyException 클래스를 교체하는 다음 코드 조각을 사용할 수 있습니다.
<?php
/**
* 사용자 예외 클래스 정의하기
*/
class MyException extends Exception
{
// 예외를 재정의해서 메시지를 필수값으로 만듭니다
public function __construct($message, $code = 0) {
// 처리할 코드
// 모든 값이 할당되도록 합니다
parent::__construct($message, $code);
}
// 객체의 사용자 문자열 표현
public function __toString() {
return __CLASS__ . ": [{$this->code}]: {$this->message}\n";
}
public function customFunction() {
echo "A custom function for this type of exception\n";
}
}
?>
add a note
User Contributed Notes 8 notes
iamhiddensomewhere at gmail dot com ¶
14 years ago
sapphirepaw.org ¶
14 years ago
Support for exception linking was added in PHP 5.3.0. The getPrevious() method and the $previous argument to the constructor are not available on any built-in exceptions in older versions of PHP.
michaelrfairhurst at gmail dot com ¶
11 years ago
Custom exception classes can allow you to write tests that prove your exceptions
are meaningful. Usually testing exceptions, you either assert the message equals
something in which case you can't change the message format without refactoring,
or not make any assertions at all in which case you can get misleading messages
later down the line. Especially if your $e->getMessage is something complicated
like a var_dump'ed context array.
The solution is to abstract the error information from the Exception class into
properties that can be tested everywhere except the one test for your formatting.
<?php
class TestableException extends Exception {
private $property;
function __construct($property) {
$this->property = $property;
parent::__construct($this->format($property));
}
function format($property) {
return "I have formatted: " . $property . "!!";
}
function getProperty() {
return $this->property;
}
}
function testSomethingThrowsTestableException() {
try {
throw new TestableException('Property');
} Catch (TestableException $e) {
$this->assertEquals('Property', $e->getProperty());
}
}
function testExceptionFormattingOnlyOnce() {
$e = new TestableException;
$this->assertEquals('I have formatted: properly for the only required test!!',
$e->format('properly for the only required test')
);
}
?>
Hayley Watson ¶
5 years ago
Check the other SPL Exception classes and extend one of those if your intended exception is a subclass of one of those. This allows more finesse when catching.
Dor ¶
12 years ago
It's important to note that subclasses of the Exception class will be caught by the default Exception handler
<?php
/**
* NewException
* Extends the Exception class so that the $message parameter is now mendatory.
*
*/
class NewException extends Exception {
//$message is now not optional, just for the extension.
public function __construct($message, $code = 0, Exception $previous = null) {
parent::__construct($message, $code, $previous);
}
}
/**
* TestException
* Tests and throws Exceptions.
*/
class TestException {
const NONE = 0;
const NORMAL = 1;
const CUSTOM = 2;
public function __construct($type = self::NONE) {
switch ($type) {
case 1:
throw new Exception('Normal Exception');
break;
case 2:
throw new NewException('Custom Exception');
break;
default:
return 0; //No exception is thrown.
}
}
}
try {
$t = new TestException(TestException::CUSTOM);
}
catch (Exception $e) {
print_r($e); //Exception Caught
}
?>
Note that if an Exception is caught once, it won't be caught again (even for a more specific handler).
shaman_master at list dot ru ¶
9 years ago
Use this example for not numeric codes:
<code>
<?php
class MyException extends Exception
{
/**
* Creates a new exception.
*
* @param string $message Error message
* @param mixed $code The exception code
* @param Exception $previous Previous exception
* @return void
*/
public function __construct($message = '', $code = 0, Exception $previous = null)
{
// Pass the message and integer code to the parent
parent::__construct((string)$message, (int)$code, $previous);
// @link http://bugs.php.net/39615 Save the unmodified code
$this->code = $code;
}
}
</code>
florenxe ¶
8 years ago
I just wanted to add that "extends" is same concept of "Inheritance" or "Prototyping in Javascript". So when you extend a class, you are simply inheriting the class's methods and properties. So you can create custom classes from existing classes like extending the array class.
paragdiwan at gmail dot com ¶
15 years ago
I have written similar simple custom exception class. Helpful for newbie.
<?php
/*
This is written for overriding the exceptions.
custom exception class
*/
error_reporting(E_ALL-E_NOTICE);
class myCustomException extends Exception
{
public function __construct($message, $code=0)
{
parent::__construct($message,$code);
}
public function __toString()
{
return "<b style='color:red'>".$this->message."</b>";
}
}
class testException
{
public function __construct($x)
{
$this->x=$x;
}
function see()
{
if($this->x==9 )
{
throw new myCustomException("i didnt like it");
}
}
}
$obj = new testException(9);
try{
$obj->see();
}
catch(myCustomException $e)
{
echo $e;
}
?>
