PHP has an exception model similar to that of other programming
languages. An exception can be throw
n, and caught ("catch
ed") 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 throw
n (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.
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.
The Standard PHP Library (SPL) provides a good number of built-in exceptions.
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"