Valid characters for actions, hooks and filters

2 Views

I haven’t ever seen a tag such as do_action('something_10'). Is it invalid if I use numbers?

If the method is valid, how can I write different numbers in the tag string conditionally? For example, is the following code correct($grade is the number)?

do_action("new_grade_$grade")
Post Views: 2

Related posts

Leave a Reply

2 comments

    1. When you “hook”/add_action/*_filter('whatever'); a callback function to do_action('whatever');, then you basically add the function (or object-method) name to the global $wp_filters-array.

    2. Doing so, you add the function/method name to an array that is built like the following

      $wp_filter[ $tag ][ $priority ][ $idx ]
// $tag = action/filter name
// $priority = 3rd argument / execution order
// $idx = "unique" name
    3. Not the 3rd argument/$idx is built using the _wp_filter_build_unique_id() function, that takes the first args from add_action/*_filter().
    4. Inside this function, every function name stays the same, only method names change. This is the reason, why you often find “funky” method names, prefixed with a pretty long number.

    Can I add numbers after letters in do_action tag?

    So yes, numbers are completely valid when naming action hooks. Summed up, it’s save to use a-zA-Z0-9_ as function/method/variable names. - is not supported. And while some characters might work well on your system, it mostly depends on the encoding if your chosen function name (example: _wUT?a_nice_DÄY!()) works or not. WordPress itself does not check if a function/var/hook/filter/whatever name is valid or not.

    Addition to @BrianFegter answer about “contextual hooks”.

    You can see some “contextual hooks”, when you take a look at the »help«-panel in (any) screen in your (MU or single) installation, using this plugin1).

    enter image description here
    enter image description here

    1) Plugin inspired by @StephenHarris article.

  2. Yes, you can dynamically create your own action hooks. WordPress has several dynamic hooks like admin_head-hookname and admin_footer-hookname. new_grade_$n is a valid hook name.