Monday, January 19, 2009

Extending Exceptions in PHP

Exceptions

Extending Exceptions
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 exeptions. 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().

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.

Example Throwing an Exception

getMessage(), "\n";
}

// Continue execution
echo 'Hello World';
?>
The above example will output:

0.2
Caught exception: Division by zero.
Hello World

Example Nested Exception

getMessage());
}
}
}

$foo = new Test;
$foo->testing();

?>
The above example will output:

string(4) "foo!"

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