PHP Exception

A new object oriented way of dealing with errors came with PHP 5. Exceptions are important and provides a better control over error handling.
Lets explain three new keywords related to exceptions:
Try - A function using an exception should be in a "try" block. If the exception does not trigger, the code will continue as normal. However if the exception triggers, an exception is "thrown".
Throw - This is how you trigger an exception. Each "throw" must have at least one "catch".
Catch - - A "catch" block retrieves an exception and creates an object containing the exception information.
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” .
You can define your own custom exception handler. Use following function to set a user-defined exception handler function.
string set_exception_handler ( callback $exception_handler )
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