Exceptions

Table of Contents

PHP 5 has an exception model similar to that of other programming languages. An exception can be thrown, and caught ("catched") within PHP. Code may be surrounded in a try block, to facilitate the catching of potential exceptions. Each try must have at least one corresponding catch block. Multiple catch blocks can be used to catch different classes of exceptions. 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. Exceptions can be thrown (or re-thrown) within a catch block.

When an exception is thrown, code following the statement will not be executed, and PHP will attempt to find the first matching catch block. 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().

In PHP 5.5 and later, a finally block may also be specified after the catch blocks. Code within the finally block will always be executed after the try and catch blocks, regardless of whether an exception has been thrown, and before normal execution resumes.

The thrown object must be an instance of the Exception class or a subclass of Exception. Trying to throw an object that is not will result in a PHP Fatal Error.

Note:

Internal PHP functions mainly use Error reporting, only modern Object oriented extensions use exceptions. However, errors can be simply translated to exceptions with ErrorException.

Tip

The Standard PHP Library (SPL) provides a good number of built-in exceptions.

Example #1 Throwing an Exception

<?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";
}

// Continue execution
echo "Hello World\n";
?>

The above example will output:

0.2
Caught exception: Division by zero.
Hello World

Example #2 Exception handling with a finally block

<?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";
}

// Continue execution
echo "Hello World\n";
?>

The above example will output:

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

Example #3 Nested Exception

<?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();

?>

The above example will output:

string(4) "foo!"

Коментарии

‘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).
2008-10-21 15:13:17
http://php5.kiev.ua/manual/ru/language.exceptions.html
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}
2009-05-27 15:19:13
http://php5.kiev.ua/manual/ru/language.exceptions.html
Автор:
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());
}
?>
2011-05-05 04:18:51
http://php5.kiev.ua/manual/ru/language.exceptions.html
Автор:
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/>";
   }

 
?>
2011-11-28 23:36:00
http://php5.kiev.ua/manual/ru/language.exceptions.html
Автор:
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
2013-06-24 21:13:34
http://php5.kiev.ua/manual/ru/language.exceptions.html
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
?>
2014-06-18 15:34:04
http://php5.kiev.ua/manual/ru/language.exceptions.html
Автор:
Contrary to the documentation it is possible in PHP 5.5 and higher use only try-finally blocks without any catch block.
2014-12-04 15:45:20
http://php5.kiev.ua/manual/ru/language.exceptions.html
Автор:
#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.
2015-04-04 05:47:31
http://php5.kiev.ua/manual/ru/language.exceptions.html
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($errstrE_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();
    }
?>
2017-06-15 13:12:33
http://php5.kiev.ua/manual/ru/language.exceptions.html
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 );
}

?>
2017-09-22 16:13:37
http://php5.kiev.ua/manual/ru/language.exceptions.html
<?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 !"
2018-02-24 11:49:41
http://php5.kiev.ua/manual/ru/language.exceptions.html
Easy to understand `finally`.
<?php
try {
    try {
        echo 
"before\n";
       
0;
        echo 
"after\n";
    } finally {
        echo 
"finally\n";
    }
} catch (
\Throwable) {
    echo 
"exception\n";
}
?>
# Print:
before
finally
exception
2023-09-08 06:11:25
http://php5.kiev.ua/manual/ru/language.exceptions.html
Автор:
As noted elsewhere, throwing an exception from the `finally` block will replace a previously thrown exception. But the original exception is magically available from the new exception's `getPrevious()`.

<?php
try {
    try {
        throw new 
RuntimeException('Exception A');
    } finally {
        throw new 
RuntimeException('Exception B');
    }
}
catch (
Throwable $exception) {
    echo 
$exception->getMessage(), "\n";
   
// 'previous' is magically available!
   
echo $exception->getPrevious()->getMessage(), "\n";
}
?>

Will print:

Exception B
Exception A
2024-01-19 10:24:31
http://php5.kiev.ua/manual/ru/language.exceptions.html

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