How do do_action and add_action work?

Question

I am trying to find what exactly do_action and add_action works. I already examine with add_action but for do_action i am trying as new now. This what i tried.

function mainplugin_test() {  $regularprice = 50;  if(class_exists('rs_dynamic')) { $regularprice = 100; }  // and doing further //like i echoing the regular price echo $regularprice; //It print 100 from this code  } 

Now instead of placing few code in main file i am planning to create do_action to avoid code messing issue.

    function mainplugin_test() {      $regularprice = 50;      do_action('testinghook');  // and doing further //like i echoing the regular price echo $regularprice; //It should print 100 but it print 50      } 

so i created another function to point out that hook as something like

function anothertest() { if(class_exists('rs_dynamic')) { $regularprice = 100; } } add_action('testinghook','anothertest'); 

Not sure how to add the lines of code to that hook that above function may work? As per i tried in my testing environment nothing helps. If i understand correct do_action is more like including a file??? If not please advise me.

Thanks.

Answer 1

do_action creates an action hook, add_action executes hooked functions when that hook is called.

For example, if you add the following in your theme's footer:

do_action( 'my_footer_hook' ); 

You can echo content at that location from functions.php or a custom plugin:

add_action( 'my_footer_hook', 'my_footer_echo' ); function my_footer_echo(){     echo 'hello world'; } 

You can also pass variables to a hook:

do_action( 'my_footer_hook', home_url( '/' ) ); 

Which you can use in the callback function:

add_action( 'my_footer_hook', 'my_footer_echo', 10, 1 ); function my_footer_echo( $url ){     echo "The home url is $url"; } 

In your case, you're probably trying to filter the value based on a condition. That's what filter hooks are for:

function mainplugin_test() {     echo apply_filters( 'my_price_filter', 50 ); }  add_filter( 'my_price_filter', 'modify_price', 10, 1 ); function modify_price( $value ) {     if( class_exists( 'rs_dynamic' ) )         $value = 100;     return $value; } 

Reference

• add_action()
• do_action()
• add_filter()
• apply_filters()

Edit (updated references links)