Find WordPress hooks and filters using Vim or similar

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WordPress allows you to extend its core using “hooks” and “filters.” For example, to execute something quite early in the execution process I may write 

add_action( 'init', function() { // Do something } );

Filters work similarly. The function that defines a hook is do_action, so to create the init hook a core developer wrote

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do_action( 'init' );

do_action accepts several optional arguments that this hook doesn’t demonstrate. The function names for filters are add_filter and apply_filter.

Say I’m browsing the source code of some plugin and it’s using a hook from one of the source files and I don’t know which one. What is the easiest way to locate it?

In Vim I use ctags a lot and I was hoping that it was possible to do something similar, only instead of giving the function name I could give the filter or hook name. Any ideas?

(If it can’t be done from within Vim, like ctags, second best would be to run a command that will locate the script for me. This could also be acceptable if it is the best solution)

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  1. Say I’m browsing the source code of some plugin and it’s using a hook
    from one of the source files and I don’t know which one. What is the
    easiest way to locate it?

    I use grep. Couldn’t work without it. grep gets me just about anything I want. grep -Rni "do_action( 'init'" * should find the ‘init’ hook. You can use regex in the search string if you need to as well as tell it to ignore particular files and/or directories. I’ve tried other options but just haven’t ever been sold on anything else. grep is quick and clean.

    This isn’t a ‘Vim’ answer but you did say ‘or similar’ 🙂

    There is a very good hook database at http://adambrown.info/p/wp_hooks/version/3.4 too.

  2. I’ve had to do this quite a lot lately so I wrote a little Vim plugin to ease the process.

    Simply place the caret on name of the hook or filter, press Leader+f to find the hooked functions, or Leader+F to find the hook/filter definition.

    To install:

    cd ~/.vim/bundle && git clone https://github.com/borzhemsky/wp-hook-finder.git

    Add the keybindings to ~/.vimrc:

    nnoremap <Leader>f :FindWPHook<CR>
nnoremap <Leader>F :FindWPHookDef<CR>

    Site note: Writing this taught me that, yes, people do things like using add_filter hook their functions to hooks defined with do_action, so searching for occurrences manually can be error-prone.

  3. From the basic to the rather involved:

    GREP

    Already explained.

    GREP FROM VIM OR VIMGREP

    If you are already in Vim, you can use the :vimgrep command or its sister :grep:

    :vim "do_action( 'init' )" **/*.php | copen

    See :help starstar for the ** wildcard that let’s you do recursive search. :vimgrep uses an internal method while :grep uses, well… grep. The latter may be faster.

    CTAGS

    Assuming you have ctags installed, the indexing can be done in the shell or in Vim:

    $ ctags -R . <-- in the shell
:!ctags -R . <-- in Vim

    and the querying is just a matter of :tag do_action. Read :help tags for an indepth explanation.

    CSCOPE

    Assuming you have cscope installed, you can use it right from the shell:

    $ cscope -R *.php

    Once the index is created you can search in cscope‘s interface and open the chosen files in your editor.

    Assuming your Vim comes with cscope support, you have to:

    1. create the index, :!cscope -bR *.php

    2. locate the index, :cs add cscope.out

    3. *f*ind the *d*efinition, :cs f d do_action

    There are other specialized tools like Codesearch or GNU Global but I think that you don’t really need to go further than plain grep or, at most, ctags.