How can I make PHP handle functions' overloading errors?

Question

Lets assume I have a class called Form. This class uses the magic method __call() to add fields to itself like so:

<?php class Form { private $_fields = array(); public function __call($name, $args) { // Only allow methods which begin with 'add' if ( preg_match('/^add/', $name) ) { // Add a new field } else { // PHP throw the default 'undefined method' error } } }

My problem is that I can't figure out how to make PHP handle the calls to undefined methods in it's default way. Of course, the default behavior can be mimicked in many ways, for example I use the following code right now:

trigger_error('Call to undefined method ' . __CLASS__ . '::' . $function, E_USER_ERROR);

But I don't like this solution because the error itself or its level might change in the future, so is there a better way to handle this in PHP?

Update Seems like my question is a little vague, so to clarify more... How can I make PHP throw the default error for undefined methods without the need to supply the error and it's level? The following code won't work in PHP, but it's what I'm trying to do:

// This won't work because my class is not a subclass. If it were, the parent would have // handled the error parent::__call($name, $args); // or is there a PHP function like... trigger_default_error(E_Undefined_Method);

If anyone is familiar with ruby, this can be achieved by calling the super method inside method_missing. How can I replicate that in PHP?

Phil · Accepted Answer · 2011-08-18 23:42:43Z

1

Use exceptions, that's what they're for

public function __call($name, $args) { // Only allow methods which begin with 'add' if ( preg_match('/^add/', $name) ) { // Add a new field } else { throw new BadMethodCallException('Call to undefined method ' . __CLASS__ . '::' . $name); } }

This is then trivially easy to catch

try { $form->foo('bar'); } catch (BadMethodCallException $e) { // exception caught here $message = $e->getMessage(); }

answered Aug 18, 2011 at 23:42

Phil

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4 Comments

Maher4Ever Over a year ago

Thanks, but this still means that I have to supply the error message. I want PHP to use its default one.

Phil Over a year ago

@Maher4Ever Why? It's your class, not PHP's. You could always omit the message all together, that exception is pretty self-descriptive

Maher4Ever Over a year ago

If I want to hide how the class is implemented, I would have to generate a message that looks exactly like the one php uses, so that calling an undefined method would show the default error. That seems like repeating what php already does... I only want to access the default message and show it!

Phil Over a year ago

@Maher4Ever Hide it from whom? It's obvious your class is not a built-in one so why should it be any surprise that it has its own error messages? AFAIK, the PHP error messages are not available as a language resource or anything like that

genesis · Accepted Answer · 2011-08-18 23:40:27Z

If you want to change error level, just change it when necessary or add if statement instead of E_USER_ERROR

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