Title: add_action & function values
Last modified: August 19, 2016

---

# add_action & function values

 *  [TrevorNet](https://wordpress.org/support/users/trevornet/)
 * (@trevornet)
 * [15 years, 4 months ago](https://wordpress.org/support/topic/add_action-function-values/)
 * I know this has been covered time and again, but most of the threads are closed
   or come close to my question without a definitive answer.
 * I understand add_action. At least the first 3 params of the add_action call itself.
   What I am not understanding is how the 4th param translates into actual values
   passed to the named function. Say I have a function called liquid_rain that takes
   3 parameters.
 *     ```
       function liquid_rain($param1, $param2, $param3) {
        // Do something with the params.
       }
       ```
   
 * From a random plug-in or my theme functions.php file I have the following line:
   `
   add_action('save_post','liquid_rain', 8, 3)`
 * How does add_action(x,x,x,**3**) translate into the actual param values for liquid_rain?
   Simply calling the function through add_action does not (it appears) assign the
   required values. Further more, what if the values for liquid_rain come from a
   source other than a form. Say – as a reaction to a conditional.

Viewing 2 replies - 1 through 2 (of 2 total)

 *  [Mark / t31os](https://wordpress.org/support/users/t31os_/)
 * (@t31os_)
 * [15 years, 4 months ago](https://wordpress.org/support/topic/add_action-function-values/#post-1881476)
 * The fourth parameter simply tells WordPress how many args the callback function
   can accept.
 * The action or filter you’re hooking onto ultimately decides how many variables
   it will pass to your action or filter callback function.
 * Imagine for a second this is your callback function.
 *     ```
       function my_func( $one, $two, $three, $four ) {
          // Doing something
       }
       ```
   
 * And now imagine you’re going to attach that function to a WP filter, and also
   let’s say for a moment this is how the code looks in WordPress.
 *     ```
       // Code sample 1
       $a = 1;
       $b = 2;
       apply_filters( 'my_filter_hook', $a, $b );
       ```
   
 * Now let’s say we attach the function onto that hook and tell WP we can support
   4 arguments, eg..
 *     ```
       add_filter( 'my_filter_hook', 'my_func', 10, 4 );
       ```
   
 * Since the hook has only provided two variables, the callback function will only
   receive data in the first two args, ie. `$one` and `$two`..
 * If instead the imaginary core code looked like this..
 *     ```
       // Code sample 2
       $a = 1;
       $b = 2;
       $c = 3;
       $d = 4;
       apply_filters( 'my_filter_hook', $a, $b, $c, $d );
       ```
   
 * We’d then find the hook has passed on data to all four of the callback functions
   args `$one`, `$two`, `$three` and `$four`.
 * I’m not sure how else to explain it without making it more confusing, so i hope
   that helps.. 😉
 *  Thread Starter [TrevorNet](https://wordpress.org/support/users/trevornet/)
 * (@trevornet)
 * [15 years, 4 months ago](https://wordpress.org/support/topic/add_action-function-values/#post-1881489)
 * Ha! I am already a bit confused, but your response helps clear things up. Finding
   the relationship between the various parts of WordPress has been very interesting
   to say the least. Thank You!

Viewing 2 replies - 1 through 2 (of 2 total)

The topic ‘add_action & function values’ is closed to new replies.

## Tags

 * [add_action](https://wordpress.org/support/topic-tag/add_action/)
 * [functions](https://wordpress.org/support/topic-tag/functions/)
 * [parameters](https://wordpress.org/support/topic-tag/parameters/)

 * In: [Hacks](https://wordpress.org/support/forum/plugins-and-hacks/hacks/)
 * 2 replies
 * 2 participants
 * Last reply from: [TrevorNet](https://wordpress.org/support/users/trevornet/)
 * Last activity: [15 years, 4 months ago](https://wordpress.org/support/topic/add_action-function-values/#post-1881489)
 * Status: not resolved

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