Thoughts filed in: Drupal

Hook soup

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Of late, I seem to keep stumbling upon Drupal hooks that I've never heard of before. For example, I was just reading a blog post about what you can't modify in a _preprocess() function, when I saw mention of hook_theme_registry_alter(). What a mouthful. I ain't seen that one 'til now. Is it just me, or are new hooks popping up every second day in Drupal land? This got me wondering: exactly how many hooks are there in Drupal core right now? And by how much has this number changed over the past few Drupal versions? Since this information is conveniently available in the function lists on, I decided to find out for myself. I counted the number of documented hook_foo() functions for Drupal core versions 4.7, 5, 6 and 7 (HEAD), and this is what I came up with (in pretty graph form):

Drupal hooks by core version
Drupal hooks by core version

And those numbers again (in plain text form):

  • Drupal 4.7: 41
  • Drupal 5: 53
  • Drupal 6: 72
  • Drupal 7: 183

Aaaagggghhhh!!! Talk about an explosion — what we've got on our hands is nothing less than hook soup. The rate of growth of Drupal hooks is out of control. And that's not counting themable functions (and templates) and template preprocessor functions, which are the other "magically called" functions whose mechanics developers need to understand. And as for hooks defined by contrib modules — even were we only counting the "big players", such as Views — well, let's not even go there; it's really too massive to contemplate.

Installing the uploadprogress PECL extension on Leopard

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The uploadprogress PECL extension is a PHP add-on that allows cool AJAX uploading like never before. Version 3 of Drupal's FileField module is designed to work best with uploadprogress enabled. As such, I found myself installing a PECL extension for the first time. No doubt, many other Drupal developers will soon be finding themselves in the same boat.

Unfortunately, for those of us on Mac OS X 10.5 (Leopard), installing uploadprogress ain't all smooth sailing. The problem is that the extension must be compiled from source in order to be installed; and on Leopard machines, which all run on a 64-bit processor, it must be compiled as a 64-bit binary. However, the gods of Mac (in their infinite wisdom) decided to include with Leopard (after Xcode is installed) a C compiler that still behaves in the old-school way, and that by default does its compilation in 32-bit mode. This is a right pain in the a$$, and if you're unfamiliar with the consequences of it, you'll likely see a message like this coming up in your Apache error log when you try to install uploadprogress and restart your server:

PHP Warning:  PHP Startup: Unable to load dynamic library '/usr/local/php5/lib/php/extensions/no-debug-non-zts-20060613/' - (null) in Unknown on line 0

Hmmm… (null) in Unknown on line 0. WTF is that supposed to mean? (You ask). Well, it means that the extension was compiled for the wrong environment; and when Leopard tries to execute it, a low-level error called a segmentation fault occurs. In short, it means that your binary is $#%&ed.

But fear not, Leopard PHP developers! Read on for some instructions for how to install uploadprogress by compiling it as a 64-bit binary.

Self-referencing symlinks can hang your IDE

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One of my current Drupal projects has been giving me a headache lately, due to a small but very annoying problem. My PHP development tools of choice, at the moment, are Eclipse PDT and TextMate. Both of these generally work great for me. I prefer TextMate if I have the choice (better config options + much more usable), but I switch to Eclipse whenever I need a good debugger (or a bit of contextual help / autocomplete). However, they haven't been working well for me in this case. Every time I try to load in the source code for this one particular project, the IDE either hangs indefinitely (in Eclipse), or it slows down to a crawl (in TextMate). I've been tearing my hair out, trying to work out the cause of this problem, which has forced me to edit individual files for several weeks, and which has meant that I can't have a debugger or an IDE workspace for this project. Finally, I've nailed it: self-referencing symlinks are the culprit.

The project is a Drupal multisite setup, and like most multisite setups, it uses a bunch of symlinks in order for multiple subdomains to share a single codebase. For each subdomain, I create a symlink that points to the directory in which it resides; in effect, each symlink points to itself. When Apache comes along, it treats a symlink as the "directory" for a subdomain, and it follows it. By the time Drupal is invoked, we're in the root of the Drupal codebase shared by all the subdomains. Everything works great. All our favourite friends throw a party. Champagne bottles pop.

The bash command to create the symlinks is pretty simple — for each symlink, it looks something like this:

ln -s . subdomain

Unfortunately, a symlink like this does not play well with certain IDEs that try to walk your filesystem. When they hit such a symlink, they get stuck infinitely recursing (or at least, they keep recursing for a long time before they give up). The solution? Simple: delete such symlinks from your development environment. If this is what's been dragging your system down, then removing them will instantly cure all your woes. For each symlink, deleting it is as simple as:

rm subdomain

(Don't worry, deleting a symlink doesn't also delete the thing that it's pointing at).

Deployment and migration: hot at DrupalCon DC

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There was no shortage of kick-a$$ sessions at the recent DrupalCon DC. The ones that really did it for me, however, were those that dealt with the thorny topic of deployment and migration. This is something that I've been thinking about for quite a long time, and it's great to see that a lot of other Drupal people have been doing likewise.

The thorniness of the topic is not unique to Drupal. It's a tough issue for any system that stores a lot of data in a relational database. Deploying files is easy: because files can be managed by any number of modern VCSes, it's a snap to version, to compare, to merge and to deploy them. But none of this is easily available when dealing with databases. The deployment problem is similar for all of the popular open source CMSes. There are also solutions available for many systems, but they tend to vary widely in their approach and in their effectiveness. In Drupal's case, the problem is exacerbated by the fact that a range of different types of data are stored together in the database (e.g. content, users, config settings, logs). What's more, different use cases call for different strategies regarding what to stage, and what to "edit live".

Read on to find out about:

  • Context, Spaces and Exportables
  • Deploy module
  • Other solutions presented
  • How we've come a long way

First DrupalCamp Australia was a success

A few weeks ago (on Sat 18th Oct 2008), we (a.k.a. the Sydney Drupal Users' Group) held the first ever DrupalCamp Australia. Sorry for the late blog post — but hey, better late than never. This was Sydney's second full-day Drupal event, and as with the first one (back in May), it was held at the University of Sydney (many thanks to Jim Woulfe from the Faculty of Pharmacy, for providing the venue). This was Sydney's biggest Drupal event to date: we had an incredible turnout of 50 people (that's right — we were booked out), and for part of the day we had two presentation tracks running in adjacent rooms.

DrupalCamp Australia logo
DrupalCamp Australia logo

Morning welcome to DrupalCamp Australia
Morning welcome to DrupalCamp Australia

Geeks in a room
Geeks in a room

Drupal and Apache in Vista: some tips

I bought a new laptop at the start of this year, and since then I've experienced the "privilege" pile of festering camel dung that is being a user of Windows Vista. As with most things in Vista, installing Drupal and Apache is finickier than it used to be, back on XP. When I first went through the process, I encountered a few particularly weird little gotchas, and I scribbled them down for future reference. Here are some things to look out for, when the inevitable day comes in which you too will shine the light of Drupal upon the dark and smelly abyss of Vista:

  1. Don't use the stop / start / restart Apache controls in the start menu (start > programs > Apache > control), as they are unreliable; use services.msc insetad (start > run > "services.msc").
  2. Don't edit httpd.conf through the filesystem — use the 'edit httpd.conf' icon in the start menu instead (start > programs > Apache > configure), as otherwise your saved changes may not take effect.
  3. If you're seeing the error message "http request status - fails" on Drupal admin pages, then try editing your 'c:\windows\system32\drivers\etc\hosts' file, and taking out the IPv6 mapping of localhost, as this can confuse the Windows mapping of to localhost (restart for this to take effect).
  4. Don't use Vista! If, however, you absolutely have no choice, then refer to steps 1-3.

Drupal at the 2008 Sydney CeBIT Expo

The past week has been a big one, for the small but growing Sydney Drupal Users' Group. Last week, on Tuesday through Thursday (May 20-22), we manned the first-ever Drupal stall at the annual Sydney CeBIT Expo. CeBIT is one of the biggest technology shows in Australia — and the original CeBIT in Germany is the biggest exhibition in the world. For three days, we helped "spread the word" by handing out leaflets, running lives demos, and talking the talk to the Expo's many visitors.

Ryan and James at CeBIT 2008
Ryan and James at CeBIT 2008

Drupal demo laptops at CeBIT 2008
Drupal demo laptops at CeBIT 2008

The Sunday before (May 18), we also arranged a full-day get-together at the University of Sydney, as a warm-up for CeBIT: there were a few informal presentations, and we got some healthy geeked-up discussion happening.

Drupal May 2008 meetup at Sydney Uni
Drupal May 2008 meetup at Sydney Uni

Dinner and drinks after the May 2008 Drupal meetup
Dinner and drinks after the May 2008 Drupal meetup

Useful SQL error reporting in Drupal 6

The upcoming Drupal 6 has a very small but very useful new feature, which went into CVS quietly and with almost no fanfare about 6 weeks ago. The new feature is called "useful SQL error reporting". As any Drupal developer would know, whenever you're coding away at that whiz-bang new module, and you've made a mistake in one of your module's database queries, Drupal will glare at you with an error such as this:

user warning: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'd5_node n INNER JOIN d5_users u ON u.uid = n.uid INNER JOIN d5_node_revisions r ' at line 1 query: SELECT n.nid, n.vid, n.type, n.status, n.created, n.changed, n.comment, n.promote, n.sticky, r.timestamp AS revision_timestamp, r.title, r.body, r.teaser, r.log, r.format, u.uid,, u.picture, FROMMM d5_node n INNER JOIN d5_users u ON u.uid = n.uid INNER JOIN d5_node_revisions r ON r.vid = n.vid WHERE n.nid = 1 <strong>in C:\www\drupal5\includes\ on line 172.</strong>

That message is all well and good: it tells you that the problem is an SQL syntax error; it prints out the naughty query that's causing you the problem; and it tells you that Drupal's "includes/" file is where the responsible code lies. But that last bit — about the "" file — isn't quite true, is it? Because although that file does indeed contain the code that executed the naughty query (namely, the db_query() function in Drupal's database abstraction system), that isn't where the query actually is.

In Drupal 6, this same message becomes a lot more informative:

user warning: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'd6_node n INNER JOIN d6_users u ON u.uid = n.uid INNER JOIN d6_node_revisions r ' at line 1 query: SELECT n.nid, n.vid, n.type, n.language, n.title, n.uid, n.status, n.created, n.changed, n.comment, n.promote, n.moderate, n.sticky, n.tnid, n.translate, r.nid, r.vid, r.uid, r.title, r.body, r.teaser, r.log, r.timestamp AS revision_timestamp, r.format,, FROMMM d6_node n INNER JOIN d6_users u ON u.uid = n.uid INNER JOIN d6_node_revisions r ON r.vid = n.vid WHERE n.nid = 2 <strong>in C:\www\drupal\modules\node\node.module on line 669.</strong>

This may seem like a small and insignificant new feature. But considering that a fair chunk of the average Drupal developer's debugging time is consumed by fixing SQL errors, it's going to be a godsend for many, many people. The value and the usefulness of this feature, for developers and for others, should not be underestimated.

GreenAsh ground-up videocast: Part III: Custom theming with Drupal 4.7

This video screencast is part III of a series that documents the development of a new, real-life Drupal website from the ground up. It shows you how to create a custom theme that gives your site a unique look-and-feel, using Drupal's built-in PHPTemplate theme engine. Tasks that are covered include theming blocks, theming CCK node types, and theming views. Video produced by GreenAsh Services, and sponsored by Hambo Design. (21:58 min — 24.1MB H.264)

I hope that all you fellow Drupalites have enjoyed this series, and I wish you a very happy new year!