Why no PHP error on call to undefined function?

Question

Whenever there is a call to an undefined function, no errors are logged. Instead the script just stops executing. To make things worse, if I run php -l filename.php, It shows that there are no syntax errors. I am using a custom error handler function, but even the first line is never reached.

How can I get it to run my error handler when there is a call to an undefined function?

I am using PHP 5.3.2-1. Here is the code that is setting the error handler:

error_reporting(-1);
$old_error_handler = set_error_handler( "userErrorHandler" );
set_exception_handler('exception_handler');

Neither the error handler nor the exception handler are being reached, although they do work for other errors.

The reason I want this is I end up having to place debug statements in my code to see how far it gets before it stops executing which is a slow process compared to an error message that would tell me the file and line number where the error is.

Answer 1

Fatal errors can not be caught by a user error handler.

See http://php.net/manual/en/function.set-error-handler.php

Specifically the part:

The following error types cannot be handled with a user defined function: E_ERROR, E_PARSE, E_CORE_ERROR, E_CORE_WARNING, E_COMPILE_ERROR, E_COMPILE_WARNING, and most of E_STRICT raised in the file where set_error_handler() is called.

And as per the comments on the PHP manual page, one work around is to test for errors in the shutdown function:

<?php
    error_reporting(E_ALL);
    ini_set('display_errors', 0);

    function shutdown(){
        $isError = false;
        if ($error = error_get_last()){
            switch($error['type']){
                case E_ERROR:
                case E_CORE_ERROR:
                case E_COMPILE_ERROR:
                case E_USER_ERROR:
                    $isError = true;
                    break;
            }
        }

        if ($isError){
            echo "Script execution halted ({$error['message']})";
        } else {
            echo "Script completed";
        }
    }

    register_shutdown_function('shutdown');
?>

Answer 2

There is a relevant part in the manual for set_error_handler().

The following error types cannot be handled with a user defined function: E_ERROR, E_PARSE, E_CORE_ERROR, E_CORE_WARNING, E_COMPILE_ERROR, E_COMPILE_WARNING, and most of E_STRICT raised in the file where set_error_handler() is called.