예외

Table of Contents

PHP 5는 다른 프로그래밍 언어와 유사한 예외 모델을 가지고 있습니다. 예외를 throw해서, PHP 안에서 잡을(catch) 수 있습니다. 잠재적인 예외를 잡기 위해서 코드를 try 블록으로 감쌀 수 있습니다. 각 try는 최소한 하나의 catchfinally 블록을 가져야 합니다.

던지는 객체는 반드시 Exception 클래스나 Exception의 자식 클래스이여야 합니다. 다른 객체를 던질 경우 PHP Fatal 오류를 발생합니다.

catch

여러 catch 블록이 각각 다른 예외 클래스를 잡을 수 있습니다. 일반적인 실행(try 블록에서 예외를 던지지 않거나, 던져진 예외 클래스에 해당하는 catch가 존재하지 않을 경우)에서는 마지막 catch 블록 정의 이후로 진행합니다. 예외는 catch 블록 안에서 (다시) throw할 수 있습니다.

예외가 던져지면, 따라오는 구문은 실행되지 않고, PHP는 해당하는 첫번째 catch 블록을 찾습니다. 예외가 잡히지 않으면, "Uncaught Exception ..." 메세지로 PHP Fatal Error가 발생합니다. set_exception_handler()로 핸들러를 정의하여 해당 오류를 처리할 수 있습니다.

finally

PHP 5.5 이후 부터 catch 블록 이후 또는 대신하여 finally 블록을 지정할 수 있습니다. finally 블록은 예외 발생 유무와 관계 없이 trycatch 블록 이후에 항상 실행됩니다.

주의

Note:

내부 PHP 함수는 주로 오류 보고를 사용합니다. 최근의 객체 지향 확장만이 예외를 사용합니다. 그러나, 오류는 ErrorException을 사용하여 간단히 예외로 변환할 수 있습니다.

Tip

표준 PHP 라이브러리(SPL)는 여러 가지 내장 예외를 제공합니다.

예제

Example #3 예외 던지기

<?php
function inverse($x) {
    if (!
$x) {
        throw new 
Exception('Division by zero.');
    }
    return 
1/$x;
}

try {
    echo 
inverse(5) . "\n";
    echo 
inverse(0) . "\n";
} catch (
Exception $e) {
    echo 
'Caught exception: ',  $e->getMessage(), "\n";
}

// 계속 실행
echo "Hello World\n";
?>

위 예제의 출력:

0.2
Caught exception: Division by zero.
Hello World

Example #4 finally 블록과 예외 다루기

<?php
function inverse($x) {
    if (!
$x) {
        throw new 
Exception('Division by zero.');
    }
    return 
1/$x;
}

try {
    echo 
inverse(5) . "\n";
} catch (
Exception $e) {
    echo 
'Caught exception: ',  $e->getMessage(), "\n";
finally {
    echo 
"First finally.\n";
}

try {
    echo 
inverse(0) . "\n";
} catch (
Exception $e) {
    echo 
'Caught exception: ',  $e->getMessage(), "\n";
finally {
    echo 
"Second finally.\n";
}

// 계속 실행
echo "Hello World\n";
?>

위 예제의 출력:

0.2
First finally.
Caught exception: Division by zero.
Second finally.
Hello World

Example #5 중첩 예외

<?php

class MyException extends Exception { }

class 
Test {
    public function 
testing() {
        try {
            try {
                throw new 
MyException('foo!');
            } catch (
MyException $e) {
                
// rethrow it
                
throw $e;
            }
        } catch (
Exception $e) {
            
var_dump($e->getMessage());
        }
    }
}

$foo = new Test;
$foo->testing();

?>

위 예제의 출력:

string(4) "foo!"
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User Contributed Notes 12 notes

up
97
ask at nilpo dot com
12 years ago
If you intend on creating a lot of custom exceptions, you may find this code useful.  I've created an interface and an abstract exception class that ensures that all parts of the built-in Exception class are preserved in child classes.  It also properly pushes all information back to the parent constructor ensuring that nothing is lost.  This allows you to quickly create new exceptions on the fly.  It also overrides the default __toString method with a more thorough one.

<?php
interface IException
{
   
/* Protected methods inherited from Exception class */
   
public function getMessage();                 // Exception message
   
public function getCode();                    // User-defined Exception code
   
public function getFile();                    // Source filename
   
public function getLine();                    // Source line
   
public function getTrace();                   // An array of the backtrace()
   
public function getTraceAsString();           // Formated string of trace
   
    /* Overrideable methods inherited from Exception class */
   
public function __toString();                 // formated string for display
   
public function __construct($message = null, $code = 0);
}

abstract class
CustomException extends Exception implements IException
{
    protected
$message = 'Unknown exception';     // Exception message
   
private   $string;                            // Unknown
   
protected $code    = 0;                       // User-defined exception code
   
protected $file;                              // Source filename of exception
   
protected $line;                              // Source line of exception
   
private   $trace;                             // Unknown

   
public function __construct($message = null, $code = 0)
    {
        if (!
$message) {
            throw new
$this('Unknown '. get_class($this));
        }
       
parent::__construct($message, $code);
    }
   
    public function
__toString()
    {
        return
get_class($this) . " '{$this->message}' in {$this->file}({$this->line})\n"
                               
. "{$this->getTraceAsString()}";
    }
}
?>

Now you can create new exceptions in one line:

<?php
class TestException extends CustomException {}
?>

Here's a test that shows that all information is properly preserved throughout the backtrace.

<?php
function exceptionTest()
{
    try {
        throw new
TestException();
    }
    catch (
TestException $e) {
        echo
"Caught TestException ('{$e->getMessage()}')\n{$e}\n";
    }
    catch (
Exception $e) {
        echo
"Caught Exception ('{$e->getMessage()}')\n{$e}\n";
    }
}

echo
'<pre>' . exceptionTest() . '</pre>';
?>

Here's a sample output:

Caught TestException ('Unknown TestException')
TestException 'Unknown TestException' in C:\xampp\htdocs\CustomException\CustomException.php(31)
#0 C:\xampp\htdocs\CustomException\ExceptionTest.php(19): CustomException->__construct()
#1 C:\xampp\htdocs\CustomException\ExceptionTest.php(43): exceptionTest()
#2 {main}
up
66
Johan
10 years ago
Custom error handling on entire pages can avoid half rendered pages for the users:

<?php
ob_start
();
try {
   
/*contains all page logic
    and throws error if needed*/
   
...
} catch (
Exception $e) {
 
ob_end_clean();
 
displayErrorPage($e->getMessage());
}
?>
up
11
christof+php[AT]insypro.com
4 years ago
In case your E_WARNING type of errors aren't catchable with try/catch you can change them to another type of error like this:

<?php
    set_error_handler
(function($errno, $errstr, $errfile, $errline){
            if(
$errno === E_WARNING){
               
// make it more serious than a warning so it can be caught
               
trigger_error($errstr, E_ERROR);
                return
true;
            } else {
               
// fallback to default php error handler
               
return false;
            }
    });

    try {
           
// code that might result in a E_WARNING
   
} catch(Exception $e){
           
// code to handle the E_WARNING (it's actually changed to E_ERROR at this point)
   
} finally {
           
restore_error_handler();
    }
?>
up
16
Shot (Piotr Szotkowski)
13 years ago
‘Normal execution (when no exception is thrown within the try block, *or when a catch matching the thrown exception’s class is not present*) will continue after that last catch block defined in sequence.’

‘If an exception is not caught, a PHP Fatal Error will be issued with an “Uncaught Exception …” message, unless a handler has been defined with set_exception_handler().’

These two sentences seem a bit contradicting about what happens ‘when a catch matching the thrown exception’s class is not present’ (and the second sentence is actually correct).
up
5
daviddlowe dot flimm at gmail dot com
4 years ago
Starting in PHP 7, the classes Exception and Error both implement the Throwable interface. This means, if you want to catch both Error instances and Exception instances, you should catch Throwable objects, like this:

<?php

try {
    throw new
Error( "foobar" );
   
// or:
    // throw new Exception( "foobar" );
}
catch (
Throwable $e) {
   
var_export( $e );
}

?>
up
11
Simo
6 years ago
#3 is not a good example. inverse("0a") would not be caught since (bool) "0a" returns true, yet 1/"0a" casts the string to integer zero and attempts to perform the calculation.
up
16
Edu
8 years ago
The "finally" block can change the exception that has been throw by the catch block.

<?php
try{
        try {
                throw new \
Exception("Hello");
        } catch(\
Exception $e) {
                echo
$e->getMessage()." catch in\n";
                throw
$e;
        } finally {
                echo
$e->getMessage()." finally \n";
                throw new \
Exception("Bye");
        }
} catch (\
Exception $e) {
        echo
$e->getMessage()." catch out\n";
}
?>

The output is:

Hello catch in
Hello finally
Bye catch out
up
5
mlaopane at gmail dot com
3 years ago
<?php

/**
* You can catch exceptions thrown in a deep level function
*/

function employee()
{
    throw new \
Exception("I am just an employee !");
}

function
manager()
{
   
employee();
}

function
boss()
{
    try {
       
manager();
    } catch (\
Exception $e) {
        echo
$e->getMessage();
    }
}

boss(); // output: "I am just an employee !"
up
6
telefoontoestel at nospam dot org
7 years ago
When using finally keep in mind that when a exit/die statement is used in the catch block it will NOT go through the finally block.

<?php
try {
    echo
"try block<br />";
    throw new
Exception("test");
} catch (
Exception $ex) {
    echo
"catch block<br />";
} finally {
    echo
"finally block<br />";
}

// try block
// catch block
// finally block
?>

<?php
try {
    echo
"try block<br />";
    throw new
Exception("test");
} catch (
Exception $ex) {
    echo
"catch block<br />";
    exit(
1);
} finally {
    echo
"finally block<br />";
}

// try block
// catch block
?>
up
2
Sawsan
10 years ago
the following is an example of a re-thrown exception and the using of getPrevious function:

<?php

$name
= "Name";

//check if the name contains only letters, and does not contain the word name

try
   {
   try
     {
      if (
preg_match('/[^a-z]/i', $name))
       {
           throw new
Exception("$name contains character other than a-z A-Z");
       }  
       if(
strpos(strtolower($name), 'name') !== FALSE)
       {
          throw new
Exception("$name contains the word name");
       }
       echo
"The Name is valid";
     }
   catch(
Exception $e)
     {
     throw new
Exception("insert name again",0,$e);
     }
   }

catch (
Exception $e)
   {
   if (
$e->getPrevious())
   {
    echo
"The Previous Exception is: ".$e->getPrevious()->getMessage()."<br/>";
   }
   echo
"The Exception is: ".$e->getMessage()."<br/>";
   }

?>
up
-2
Daan
5 months ago
I would like to emphasise that you can not rethrow an Exception inside a catch-block and expect that the next catch-block will handle it.

<?php

try {
    throw new
RuntimeException('error');           
} catch (
RuntimeException $e) {
    throw
$e;
} catch (
Exception $e) {
   
// this will not be executed[
}
?>
up
-1
Tom Polomsk
7 years ago
Contrary to the documentation it is possible in PHP 5.5 and higher use only try-finally blocks without any catch block.
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