(PHP 5, PHP 7)
restore_exception_handler — Restores the previously defined exception handler function
Used after changing the exception handler function using set_exception_handler(), to revert to the previous exception handler (which could be the built-in or a user defined function).
   This function always returns TRUE.
  
Example #1 restore_exception_handler() example
<?php
    function exception_handler_1(Exception $e)
    {
        echo '[' . __FUNCTION__ . '] ' . $e->getMessage();
    }
    function exception_handler_2(Exception $e)
    {
        echo '[' . __FUNCTION__ . '] ' . $e->getMessage();
    }
    set_exception_handler('exception_handler_1');
    set_exception_handler('exception_handler_2');
    restore_exception_handler();
    throw new Exception('This triggers the first exception handler...');
?>
The above example will output:
[exception_handler_1] This triggers the first exception handler...