The CakePHP form save, validate, and debug problem

CakePHP form save/validate/debug FAQ: How do I debug problems in the CakePHP form save/validate process?

One problem I've run into with CakePHP is that while the form validation approach works very well 95% of the time, when it fails it can be very hard to debug. Because the form validation process happens when you invoke the save() method, much of this debugging process seems to be out of your control.

Digging into the CakePHP save/validate/debug problem

Here are some of the tips I've learned so far when debugging some of my most difficult CakePHP form validation problems:

• First, make sure the CakePHP 'debug' parameter (Configure::read('debug')) is set to a high value -- to 2 or 3 -- depending on your CakePHP version.
• Display Flash and Auth messages in your view pages (as shown below).
• Add debug() or log() statements to your own CakePHP form validation code.
• Use debug() or log to on $this->data.
• Use this CakePHP SQL debug technique.

One of the great things about open source tools like CakePHP is that you can also crack open their code to add your own debug statements, but I'm glad to say I haven't had to do that yet, even with a very nasty recent CakePHP Auth form validation problem.

I will expand on two of these CakePHP save/validate/debug techniques in the next two sections, but in general I'll assume you know what I'm talking about in these bullet points; please leave a note in the Comments section below if you need more information.

Also, note that the CakePHP debug, dump, log, and trace methods are documented on this debugging page in the CakePHP Cookbook.

Showing CakePHP messages in the view

If you're new to CakePHP (or just tired, like I was recently) you might not remember to show CakePHP error messages in your view pages. In either your layout page or in your individual view pages, make sure you're displaying CakePHP validation messages something like this:

<?php 
// CakePHP Flash messages ... 
if ($session->check('Message.flash')) { 
  $session->flash(); 
} 

// CakePHP Auth messages ... 
if ($session->check('Message.auth')) { 
  $session->flash('auth'); 
} 
?> 

I also just learned of this very nice way to display CakePHP validation errors from the controller:

debug($this->User->validationErrors);

Common CakePHP form validation problems

You can also get in the way of the CakePHP form validation process by modifying various CakePHP functions, including beforeSave, beforeValidate, and your own custom CakePHP form validation methods. If you've modified CakePHP beforeSave or beforeValidate, make sure you're returning 'true' from them, and in your own custom CakePHP validation methods, make sure you're returning either true or false, as the logic dictates.

The CakePHP form save(), validate, and debug problem

Unfortunately none of these approaches to debug the CakePHP save function and form validate process are perfect, but they're the only approaches I know at this time.

For a rapid resolution to the CakePHP save/validate/debug problem I feel like I'd like to put the CakePHP validate functions into a debug or stack trace mode, and then dig through the detailed output for my problem. With this current approach I feel like I'm trying to infer what the problem is from some indirect debug output, which isn't ideal.

Of course the other potential solution to the CakePHP save/validate/debug problem is to crack open the CakePHP validation helper code, but I haven't had to do that yet. Fortunately I have been able to infer my form validation problems from the output I've been able to gather, but again that output never shows "Your problem is right here", it's more of a process of looking at the data until you see something that doesn't look right, and working backwards from there.