Exceptions

Table of Contents

PHP 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 or finally block.

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.

catch

Multiple catch blocks can be used to catch different classes of exceptions. Normal execution (when no exception is thrown within the try block) 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 7.1 and later, a catch block may specify multiple exceptions using the pipe (|) character. This is useful for when different exceptions from different class hierarchies are handled the same.

finally

In PHP 5.5 and later, a finally block may also be specified after or instead of 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.

One notable interaction is between the finally block and a return statement. If a return statement is encountered inside either the try or the catch blocks, the finally block will still be executed. Moreover, the return statement is evaluated when encountered, but the result will be returned after the finally block is executed. Additionally, if the finally block also contains a return statement, the value from the finally block is returned.

Notes

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.

Examples

Example #3 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 #4 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 #5 Interaction between the finally block and return

<?php

function test() {
    try {
        throw new 
Exception('foo');
    } catch (
Exception $e) {
        return 
'catch';
    } finally {
        return 
'finally';
    }
}

echo 
test();
?>

The above example will output:

finally

Example #6 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!"

Example #7 Multi catch exception handling

<?php

class MyException extends Exception { }

class 
MyOtherException extends Exception { }

class 
Test {
    public function 
testing() {
        try {
            throw new 
MyException();
        } catch (
MyException MyOtherException $e) {
            
var_dump(get_class($e));
        }
    }
}

$foo = new Test;
$foo->testing();

?>

The above example will output:

string(11) "MyException"