20

This question might be wrong, I am not sure about it. Because I am not clear on this.

I know add_action it is used to to hook our function to the specified function. For example add_action('wp_head'.'myfunc'); now what ever code in myfunc will be executed in the wp_head(). This is clear but i am having doubt in do_action what it does?

I think it is used to create our own hook like already available hooks(wp_head,wp_footer,..etc) If i am correct can anyone show me a simple understandable answer with simple example.

I have tried the difference in internet but all are pointing to difference between add_action and add_filter. I don't want to go there because first i want to clarify this and then I’ll move there.

Can anybody help me?

EDIT after Question POST

function custom_register()
{
    echo '<script>jQuery(document).ready(function(){alert("Learning Hooks");});</script>';

}
do_action('custom');

add_action('custom','custom_register');

I tried this in plugin but i didn't get the alert message.

But when i hook the same function with wp_head then it is working fine

/******************working****************/
add_action('wp_head','custom_register');
  • What happens when you call do_action('custom'); after you registered the callback? And make sure jQuery is loaded. – fuxia Oct 28 '13 at 11:07
  • i did not get the alert message either on back end or front end – sun Oct 28 '13 at 11:12
  • jQuery are loaded. When i hook the same function with wp_head it is working fine but not with the custom – sun Oct 28 '13 at 11:28
  • Sun, I believe your original Question was answered by toscho and you should mark this as resolved. The edits #3 an #4 that you've done belong on a new Question. – brasofilo Oct 30 '13 at 13:32
11

Use do_action( 'unique_name' ) to create your own actions.

You can use that to offer an API for your plugin, so other plugins can register callbacks for your custom action. Example: Do I need to call do_action in my plugin?

But you can use custom actions (or filters) in a theme too. Example: Best practice way to implement custom sections into a WordPress theme

And you can combine both to make a plugin and a theme working together. Example: How to make method from plugin available in theme?

Summary: add_action( 'foo' ) registers a callback, do_action( 'foo' ) executes that registered callback.

  • Thanks for the help i got this is mainly for API purpose. I tried a sample but it didn't work out.Can you find any problem there? Check my EDIT @toscho – sun Oct 28 '13 at 11:07
  • Can we say this as another case like inheritance? intead of extending and overriding the class we are going this way. Is this correct? – sun Oct 28 '13 at 12:11
  • @sun Hm, yes, but you can combine both approaches, they are not mutually exclusive. – fuxia Oct 28 '13 at 12:19
1

This is my guess, so if you know better, please make a comment so I can update my guess.

Your plugin code is executed before wp_head() (which we can assume will invoke the actions added to it). When you add_action('wp_head','custom_register'), you are telling PHP that when (in the future) do_action('wp_head') is called, to call custom_register() as well. The same is true of your call to add_action('custom','custom_register') but as you see in your code, the call to do_action('custom') has already been made, and when it was called, there was not (yet) any action added to it. This is why Toscho asked what happens when you call do_action('custom') after you registered the callback. Your answer about back end and front end is ambiguous. If you swap the last two lines in the following code, I think it will work:

function custom_register()
{
    echo '<script>jQuery(document).ready(function(){alert("Learning Hooks");});</script>';

}
do_action('custom');                    // This is called before it will have an effect.

add_action('custom','custom_register'); // Too late - do_action was already called.
0

do_action : Registers an action hook while add_action : adds a callback function to the registered hook.

Example

Consider you wanted to print something before sidebar in you template.

  1. You will add an action hook in your template file index.php via <?php add_action('bp_sidebar_left'); ?>.
  2. Now in your functions.php file you can add a callback function to that hook to print something you want.

add_action('bp_sidebar_left', 'bp_sidebar_left_cb'); function bp_sidebar_left_cb() { echo 'Hello World !'; }

-1

You have to use like below:

function custom_register()
{
    echo '<script>jQuery(document).ready(function(){alert("Learning Hooks");});</script>';

}
.

add_action('custom','custom_register'); // Too late - do_action was already called. 
do_action('custom');                    // This is called before it will have an effect
  • It is working for me – user112289 Feb 1 '17 at 16:16

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