How WordPress understands what do with the (all) key in the $wp_filter array? [duplicate]
You have all explained in this function for instance File: wp-includes/plugin.php 402: /** 403: * Execute functions hooked on a specific action hook. 404: * 405: * This function invokes all functions attached to action hook `$tag`. It is 406: * possible to create new action hooks by simply calling this function, 407: * specifying … Read more