Solution:
The add action does not accept any new variables nor will it return any variables to the function that runs it. But you can access variables that are passed to the function.
function custom_function($arga){
echo $arga;
}
add_action ('callname', 'custom_function', 10, 1);// 1= number of arguments accepted, use 2 for 2 etc...must add variables to do action call
//sometime later in the code
do_action('callname', $arga);
If you want to inject variables in you have to think a little bit back to basics. If you want to access variables within functions that are not passed you have 2 options:
- Retrieve them from DB or server storage or similar
- Use the Global declaration. You can accesss all variables that are set at the time the do_action is run.
You would rarely call do_action for wordpress hooks (see note below), but you may end up in a situation where you are coding a template FILE (which runs after plugins and then after themes) and you want to keep your logic in the plugin you could add do_action()
into the template file and the actions set in the plugin will run at that point. Or similarly if you design a plugin that you want to be able to modify in the theme you could add an action to a late wp hook, within the called function, you could call do_action for your custom hook and hook functions to it in your theme. Loads of possibilities.
Whatever your logic for calling a WP hook early is, don’t if you are within the WP load pattern