Trace where code is coming from (PHP)

Question

I'm going through a customer's server, running crazy proprietary forum software (vBulletin) and even worse SEO mods (vbseo). I cannot figure out where the php code for a page is coming from! How to trace this URL back to a PHP page: http://www.example.com/forum/members/connie.html I just joined a project with the code based on a heavily modified vBullitin install with the VBSEO plugin. This particular plugin is horrific spaghetti code with tens of include()s, .htaccess redirects and possibly .httpd.conf changes. Then it pulls strings from a database so I cannot even use grep to find the code file!

Is there any way to stack-trace PHP to log all the code that runs to produce a page? I have root access but I am not supposed to stop or restart the server. A simple list of the include() hierarchy of files that went into producing the page would suffice.

Note that I cannot use debug_backtrace because I don't know where the code I'm looking for is! The debug_backtrace function is the exact opposite of what I need.

Thanks.

Answer 1

Sounds like you need to step through it with Xdebug. Most common IDE's support it such as Netbeans and PHPStorm.

Resources:

• Tracing PHP apps with Xdebug
• Xdebug with Netbeans
• Xdebug with PHPstorm (I recommend)
• Xdebug with Eclipse
• Chrome Xdebug extension (I recommend)
• Firefox Xdebug plug-in

In both the above mentioned IDE's, you can CTRL+Click a function/method and it will take you to the line in the file where it is defined. You can also track usages for both functions and variables.

Tracing code is built-in to xdebug. Here's an example from Zend:

<?php

  xdebug_start_trace('c:/data/fac.xt');

  print fac(7);

  function fac($x)
  {
    if (0 == $x) return 1;
    return $x * fac($x - 1);
  }

  xdebug_stop_trace();

?>

Trace file output:

TRACE START [2007-10-26 12:18:48]
    0.0068      53384     -> fac() C:\www\fac.php:5
    0.0069      53584       -> fac() C:\www\fac.php:10
    0.0069      53840         -> fac() C:\www\fac.php:10
    0.0070      54096           -> fac() C:\www\fac.php:10
    0.0070      54376             -> fac() C:\www\fac.php:10
    0.0071      54656               -> fac() C:\www\fac.php:10
    0.0072      54936                 -> fac() C:\www\fac.php:10
    0.0072      55216                   -> fac() C:\www\fac.php:10
    0.0073      55392     -> xdebug_stop_trace() C:\www\fac.php:13
    0.0237      55392
TRACE END   [2007-10-26 12:18:48]

Answer 2

Check out the debug_backtrace function - this should always be available, even on production servers.