Monday, 30 January 2012

Little debugging aid

I had been having a real problem tracking down a PHP error in Drupal which was passing an array to htmlspecialchars() in check_plain() instead of a string. I needed to use debug_backtrace() but the issue was related to Views which meant that the arguments being passed at higher levels were catastrophically huge.

It was a real problem, using krumo just resulted in out-of-memory errors. And the problem was also happening inside AJAX calls so any attempt to simply print the output was doomed.

I needed a way to get a function backtrace which was not too verbose, didn't crash the machine and would work in an AJAX call.

The solution is the following routine which takes a debug_backtrace() extracts only the information we need and outputs to a file. It's not Drupal-specific but you may need to set up the directory:

 * Backtrace to a file for when nothing else works
function debug_backtrace_file($fname = 'backtrace') {
  $file = fopen("c:\\tmp\\{$fname}.log", 'ab');
  if (!$file) {
  fputs($file, '=============== ' . date('Y-m-d H:i:s') . " ===============\n");
  $line = __LINE__;
  foreach (debug_backtrace() as $entry) {
    $function = $entry['function'];
    if ($function!=__FUNCTION__) {
      if (isset($entry['class']) && $entry['class']) {
        $function = "{$entry['class']}::$function";
      fputs($file, sprintf("function %s at line %d in file %s\n", $function, $line, isset($entry['file'])?$entry['file']:t('unknown')));
    $line = $entry['line'];

Happy bug hunting.

Thursday, 26 January 2012

Where the **** is it?

You know how it is? You have this complex and massive PHP structure with recursive elements and somewhere in all that is a value you're looking for. Views object I'm looking at you!

Here's a PHP routine, which is not Drupal specific, that will dig down into an object to find the property or array item you're looking for - and it avoids recursion by keeping a list of structures it's already searched by MD5ing the serialized version of the structure.

The parameters are the initial structure to search; the property you're looking for - it can be partial if you're not sure what the property is called; $id would usually be the identifier of the structure you're supplying and $depth should be ignored. It returns an array of strings that show the way into the structure to find the property. It's quite common to get multiple results.

One thing to watch out for: If your structure is recursive (like a Views object) and you start the search deeper into the structure with the idea that you'll shorten the search? Well you might, but if it's recursive you might also end up going into one of the recursed objects because the routine hasn't seen it before.

Anyway, with that in mind, here it is:

function common_locate($struct, $seek, $id = '', $depth = 0) {
  static $structs = array(), $results = array();
  if (is_array($struct) || is_object($struct)) {
    $struct = (array) $struct;
    foreach ($struct as $key => $value) {
      if (strpos($key, $seek)!==FALSE) {
        $results[] = "$id => $key = $value";
      if (is_array($value)) {
        $idx = str_replace('0', 'g', md5(serialize($value)));
        if (!isset($structs[$idx])) {
          $structs[$idx] = "$key:$depth";
          common_locate($value, $seek, "{$id}[$key]", $depth+1);
      elseif (is_object($value)) {
        $idx = str_replace('0', 'g', md5(serialize($value)));
        if (!isset($structs[$idx])) {
          $structs[$idx] = "object:$key:$depth";
          common_locate($value, $seek, "{$id}->$key", $depth+1);
  return $results;

Wednesday, 25 January 2012

Wiki filter for Drupal

One of the known problems with Drupal is no Wiki module. It is possible to put together a Wiki using various resources but the biggest stumbling block is the text filter.

There have been attempts and some successes. The current perceived wisdom is to use FlexiFilter - sorry but it's just too cumbersome. In fact nightmarish.

And I needed a Wiki filter for a project so this evening I spent 5 hours writing a Wiki filter for Drupal 7.

Does pretty much everything you could want including nested OL/UL lists which can be mixed - I only mention that particularly because it was a bitch. Otherwise it's got italics, bold, underline, strikethrough, h2-h6, blockquotes, code (pre), superscript and subscript.

So to set up a Wiki Text format on Drupal 7 you use these in this order:

  • Limit allowed HTML tags - to none, to clear out any tags in the text.
  • Then my filter
  • Convert line breaks
  • Assign IDs to anchors (From the TOC module)
  • Table of contents filter module
  • Freelinking module to deal with URL links

Then have WikiTools hijack Freelinking (it's an option). And configure the rest as desired.

Voila! A Drupal Wiki.

I will be putting it onto presently.

Saturday, 21 January 2012

Stable Field Value Extraction module released

Okay, after weeks of nobody complaining about any aspect of my field_extract module I have finally got around to issuing the code as the full stable version. Hurray.

Now because I'm lazy I use Eclipse for development purposes - I know, I know, how can I be a proper developer if I don't use Linux and Vim? Well, I don't. I was using command line before you were born (unless you were born before 1983). Been there, done that.

However Eclipse and Drupal Git are strange bedfellows, and it can take a bit of work learning how they can be made to work together.

Getting Drupal repos cloned locally isn't too much of an issue once you've got your SSH keys sorted out, and for cloning you can happily use http.

Pushing upstream is another matter entirely (and you will to need to use just Push... instead of Push upstream... until you get it sorted out and configured). If you try using http you may well hit a brick wall, just as I did. the trick is to use git+ssh for your protocol, and it'll work nicely. One thing, which is obvious unless you forget it, is to include Add all tags spec if you are uploading tags as well as branches. Ahem.

Hopefully it won't be so long before my next posting - I have a fun new website specifically for developers coming up. I think you're going to like it, it provides a service that all developers need from time to time, and there is only one website I've found that fulfils the need, and not as well as my version. It's written in D7 of course, leveraging it as a development framework rather than a CMS.

And with that enigma, I'll leave you.