Used to trigger a user error condition, it can be used by in conjunction with the built-in error handler, or with a user defined function that has been set as the new error handler (set_error_handler()). This function is useful when you need to generate a particular response to an exception at runtime. For example:
Anmerkung: See set_error_handler() for a more extensive example.
See also error_reporting(), set_error_handler(), restore_error_handler(), user_error()