Plugin init hook fires repeatedly

Question

I 've just noticed that the init event of a plugin I write myself keeps firing every minute or so if any dashboard's page is loaded in the browser, without interacting with it or even focus on it.

Is this behavior expected? I cant find any information about it, am I missing something ?

Answer 1

This happens because you are not excluding ajax requests.

Check this example from the WordPress Codex for the admin_init hook which is also valid for the init hook and see how AJAX requests are exluded in the if using the DOING_AJAX constant:

/**
 * Restrict access to the administration screens.
 *
 * Only administrators will be allowed to access the admin screens,
 * all other users will be shown a message instead.
 *
 * We do allow access for Ajax requests though, since these may be
 * initiated from the front end of the site by non-admin users.
 */
function restrict_admin() {

    if ( ! current_user_can( 'manage_options' ) && ( ! defined( 'DOING_AJAX' ) || ! DOING_AJAX ) ) {
        wp_die( __( 'You are not allowed to access this part of the site' ) );
    }
}
add_action( 'admin_init', 'restrict_admin', 1 );

You can use this as a starting point:

add_action( 'init', 'wpse_182220_init' );
function wpse_182220_init() {

    // Exit function if doing an AJAX request
    if ( defined( 'DOING_AJAX' ) && DOING_AJAX ) {
        return;
    }

    echo 'OK, not doing AJAX';

}

Props to RRikesh for mentioning it in his comment.