How to debug Drupal or ... How I fell in love with the debug() function

Submitted by Mindpiss on Fri, 25/01/2013 - 10:25

Let's say you see recurring error messages in your db log file and you want to try and pinpoint the issue to be able to apply a fix.
So, how do you go about debugging your code?

Well, there are many different ways. You could go old-school and use 

var_dump();

or 

print_r();

.
Or you could go a step further and use 

debug_backtrace();

to try and pinpoint the source of the error.

Alternatively of course you can always install xdebug or the Zend php debugging extension - but for most shared hosting this may be impossible.

So here are a few other options we have (i'll try and add more if and when I come across them ;-) ):

- Use the Devel Module.

- Using 

debug_backtrace();

:

Example1:

        $trace = debug_backtrace();
        $backtrace_lite = array();
        foreach( $trace as $call ) {
          $backtrace_lite[] = $call['function']."    ".$call['file']."    line ".$call['line'];
        }
        // use drupals own debug() function
        debug( $backtrace_lite, "TRACE", true );

Example 2:

        $bt = debug_backtrace();
        foreach ($bt as $key => $value) {
          if ($key == 0) {
            continue;
          }
          unset($bt[$key]['args']);
          unset($bt[$key]['object']);
        }
        drupal_set_message(str_replace('    ', '    ', nl2br(htmlentities(print_r($bt, TRUE)))));

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