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 0Exception $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_ERROR 오류가 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 0Exception $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";
    }
}
?>

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User Contributed Notes 8 notes

up
12
iamhiddensomewhere at gmail dot com
10 years ago
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.
up
4
sapphirepaw.org
10 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.
up
1
michaelrfairhurst at gmail dot com
7 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')
        );
}

?>
up
0
Hayley Watson
1 year 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.
up
-1
Dor
8 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).
up
-8
florenxe
4 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.
up
-8
shaman_master at list dot ru
5 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>
up
-21
paragdiwan at gmail dot com
11 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;
    }
?>
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