Php/docs/language.exceptions
异常处理
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 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().
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.
注释
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.
范例
Example #3 Throwing an Exception
<?phpfunction 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: ', $e->getMessage(), "\n";}// Continue executionecho "Hello World\n";?>
以上例程会输出：
0.2 Caught exception: Division by zero. Hello World
Example #4 Exception handling with a finally block
<?phpfunction inverse($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 executionecho "Hello World\n";?>
以上例程会输出：
0.2 First finally. Caught exception: Division by zero. Second finally. Hello World
Example #5 Nested Exception
<?phpclass 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();?>
以上例程会输出：
string(4) "foo!"
