Top Drupal Hooks and Functions

Alternative title: What every new Drupal developer should know

Over the past few years I've been teaching various Drupal classes ranging from introductory courses to module development courses for seasoned developers. In fact what lit a fire under me to write up this entry was an upcoming course I'm doing with Chapter Three December 14-18th in San Francisco. I'm my classes nearly every student has asked me a variation of the same question; What do I need to know?

If the student was a beginner I'd point them to one of the numerous Top X Drupal modules, such as Lullabot's Top 80, or direct them to review the awesome site showcases up on drupal.org. If the student was a developer (or aspiring developer) the answer was never as concrete. I would explain the concept of a hook, rattle off a few hooks I thought were important, point them to greggle's (or GVS's?) awesome Cheat sheet, tell them about t(), hook_menu, explain how db_query() worked, and then direct them to http://api.drupal.org. Being the geek I am this wasn't good enough for me so I set out to find out what the top hooks and functions were. I wanted something concrete.

I broke out my terminal and used CVS to checkout every module on drupal.org that was listed as stable for Drupal 6 (those in a DRUPAL-6 branch), 3,308 modules. I then wrote a quick and dirty BASH script that went through every function sorting, counting, and ultimately discovering what the most heavily used hooks were. I wrote this script over a year ago at a time when I was living behind the great firewall of China, which made blogging, twittering, and other fun Internet activities a frustrating experience, which is why I have not posted this sooner.
Without much further delay here are the top hooks used in Drupal 6:

Hook name	# of uses	Comments
hook_menu	2,120
hook_uninstall	1,659	Very brief research showed that modules were implementing hook_uninstall to remove variables set in the administrative pages or with variable_set, which would explain why this has more implementations than hook_install
hook_install	1,520
hook_perm	1,374
hook_help	1,232	Wow! This is pretty awesome
hook_theme	1,183
hook_schema	999
hook_form_alter	852
hook_nodeapi	660
admin_settings	591	This is not a hook but a common way to name your administrative settings function.

The next 12 significant implementations are:

Hook name	# of uses	Comments
hook_block	568
hook_init	538
settings	446	Related to admin_setting in the top ten
hook_form	437
hook_user	354
hook_cron	317
hook_enable	273
settings_form	265	Related to admin_setting in the top ten
hook_load	264
hook_views_api	261
hook_delete	241
hook_access	237

Most Utilized Functions

My curiosity then led me to answer the question: What are the most frequented used functions in a Drupal module?
A few commands later I discovered 143,783 unique functions used a total of 1,008,398 times across the 3,308 modules. Below is how these panned out.
Note: I removed uses of if, foreach, etc.

Function name	# of uses	Comments
array()	200,886	Proof positive Drupal developers love arrays. Note that this is technically a language construct and not a function.
t()	107,388	Hurray for translation!
db_query()	24,266	Drupal developers also love the database
variable_get()	23,694
theme()	8,283
drupal_set_message()	8,260	We love our messages
l()	7,149
isset()	6,331
db_fetch_object()	6,072	db_fetch_array came in at 1,931 uses
url()	5,087
unset()	4,654
define()	4,350
variable_del()	3,969
variable_set()	3,854
check_plain()	3,384
drupal_render()	3,321
db_result()	3,147
form_set_error()	3,111
drupal_get_path()	2,825
str_replace()	2,633

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For the curious here are the BASH commands I ran to discover this information

The completely inefficient but written in roughly ten minutes BASH script I used to discover the top hooks was: --count_functions.sh--

#!/bin/sh
module_dir="/Users/jredding/Downloads/contributions/modules"
for module_name in `find $module_dir -name *.info|xargs basename |awk -F.info '{print $1}'`
do
grep -hr "function * ${module_name}_" *|awk -F${module_name}_ '{print $2}'|awk -F"(" '{print $1}'
done

I then piped the output through

sort |uniq -c |sort -n 

Be aware that this method takes a very long time to process, roughly three to four hours. I later modified the script to the following, which only took about seven minutes to run:

functions_tmp=/tmp/all_functions.txt
module_dir="/Users/jredding/Downloads/contributions/modules"
grep -hR "^function *" modules/* > $functions_tmp

for module in `find $module_dir -name *.info|xargs basename |awk -F".info" '{print $1}'`
do
  grep -h "function * ${module}_" $functions_tmp |awk -F${module}_ '{print $2}'|awk -F"(" '{print $1}'
done
rm $functions_tmp
~                 

Of course I could probably save more time if I saved the data to two arrays and did all of this searching/sorting in memory instead of performing literally thousands of disk hits. I'll save that for another day.

To discover every function used I ran the following command:

find ./modules/ -exec awk '/[a-9]\(/ { for (i = 1; i <= NF; i++) printf "%s\n", $i }' {} \; |awk '/[a-9]\(/ {print}'|awk -F\( '{print $1}' |sort |uniq -c |sort

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A few interesting stats

I found the following stats interesting.

#	What
3,308	Total modules analyzed
67,582	Total number of defined functions
20-21	Average number of functions per module
143,783	Unique functions called including Drupal and PHP functions
1,008,398	Total functions called including Drupal and PHP functions

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Raw Data

Function use

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