WordPress Theme activation hook?

5 comments

1. You might be looking for the after_setup_theme hook:

   http://codex.wordpress.org/Plugin_API/Action_Reference/after_setup_theme

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2. For anyone stumbling upon this question; there is an action you can hook into (added 3.3.0) which is fired only on activation of a new theme: after_switch_theme

   add_action('after_switch_theme', 'mytheme_setup_options');
   
   function mytheme_setup_options () {
     //doing a thing...
   }
   

   http://codex.wordpress.org/Plugin_API/Action_Reference/after_switch_theme

   To do something on deactivation of a theme you can use the sister action: switch_theme

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3. With the theme preview features it is unlikely that there will ever be a theme activation hook since themes need to work even without being “activated”.

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4. After trying @sleepingkiwi method i encountered a problem. A client might try a different theme (even if just for a moment), this might create a problem due to the fact that the “on theme activation” hook we created ran twice.

   The best method is using after_switch_theme in concert with WordPress “update_option” to save and later check an activation noticethus making this method bullet proof.

   Example:

   add_action('after_switch_theme', 'sgx_activation_hook');
   function sgx_activation_hook() {
       if(get_option('SOMEPREFIX_theme_activated') != '1') {
   
           update_option( 'SOMEPREFIX_theme_activated', '1' );
   
           // RUN THEME_ACTIVATION STUFF HERE
   
       }
   }
   

   Hope this helps.

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5. The action hook after_switch_theme sometimes may fail because it fires only if the old theme still exists. This is written in the codex.

   You can also check it directly in wp-includes/theme.php in the function check_theme_switched() where the action hook is added. You will see that the action hook “after_switch_theme” is inside the condition if ( $old_theme->exists() ) {….}

   If you want to be sure the hook fires every time a theme is activated, and no matter if the old theme still exists, you can create your custom hook by hooking the change of the option “stylesheet”.
   Every time a theme is activated that option stores the name of the new active theme. So:

   add_action( 'update_option_stylesheet','my_theme_activation_hook',20,3 );
   add_action( 'update_site_option_stylesheet','my_theme_activation_hook',20,3 ); //For multisite installations
   
   function my_theme_activation_hook( $old_value, $value, $option ){
       //It adds an action hook after theme activation, no matter if the old theme still exists
       do_action( 'my_after_theme_activation');
   }
   

   Then you can use your action hook “my_after_theme_activation” or whatever you want to call it.

   This method is not perfect because a plugin could also update the option “stylesheet” without a real theme activation. I don’t see why they should do it, but it’s allowed, and you never know. So, I would take that into account.
   Use it if for you it’s not a problem that it fires also if a new theme is not really activated, but one of the plugins just changed the option “stylesheet”.

   You could also directly hook the change of the option “theme_switched” instead of “stylesheet”. Not tested this, but looking at the code it looks like it fires two times when you activate a new theme. The first time to save the old theme stylesheet, and a second time to save the value “false”.

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