wp_ajax_{$action}
Action Hook: Fires authenticated Ajax actions for logged-in users.
Source: wp-admin/admin-ajax.php:187
wp_ajax_nopriv_{$action}
Action Hook: Fires non-authenticated Ajax actions for logged-out users.
Source: wp-admin/admin-ajax.php:202
wp_ajax_{$_REQUEST[‘action’]}
Action Hook: Fires authenticated Ajax actions for logged-in users.
Source: wp-admin/admin-ajax.php:99
wp_ajax_nopriv_{$_REQUEST[‘action’]}
Action Hook: Fires non-authenticated Ajax actions for logged-out users.
Source: wp-admin/admin-ajax.php:114