custom_background_queue_process.php

<?php

/*
* Function to push a task for background processing
* @param: string $callbackName - Your classback acction name
* @param: mixed $payload - Your payload data that you will get when procssing on callback
*/

function my_custom_queue_on_background($callbackName, $payload)
{
    $body = [
        'payload' => $payload,
        'callback_name' => $callbackName
    ];

    $args = array(
        'timeout' => 0.1,
        'blocking' => false,
        'body' => $body,
        'cookies' => $_COOKIE,
        'sslverify' => apply_filters('https_local_ssl_verify', false),
    );

    $queryArgs = array(
        'action' => 'my_custom_callback_for_background',
        'nonce' => wp_create_nonce('my_custom_callback_for_background'),
    );

    $url = add_query_arg($queryArgs, admin_url( 'admin-ajax.php' ));
    wp_remote_post(esc_url_raw($url), $args);
}

/*
* Function to catch the self ajax request and firing the requested action
*/
function mycuctomProcessRouting() {
    $callbackName = sanitize_text_field($_REQUEST['callback_name']);
    if ( ! wp_verify_nonce( $_REQUEST['nonce'], 'my_custom_callback_for_background' ) ) {
        error_log($callbackName. ' Security Check Failed');
        die( 'Security Check Failed' );
    }
    $data = $_REQUEST['payload'];
    do_action($callbackName, $data);
    echo 'success';
    die();
}

// Here we will catch the self ajax request and and route the handler
add_action('wp_ajax_my_custom_callback_for_background', 'mycuctomProcessRouting');
add_action('wp_ajax_nopriv_my_custom_callback_for_background', 'mycuctomProcessRouting');