Looking for a hook for post.php
You can add your code to the init action hook and check global $pagenow variable: add_action( ‘init’, ‘wpse8170_check_from_var’ ); function wpse8170_check_from_var() { global $pagenow; if ( ‘post.php’ != $pagenow || ! isset( $_GET[‘post’] ) || ! isset( $_GET[‘from’] ) || 1 != (int) $_GET[‘from’] ) { return; } update_post_meta( (int) $_GET[‘post’], ‘EDITED’, ‘true’ ); }