WP mobile redirect for AMP

functions.php

<?php 

function wp_ampify_template_redirect(){
  if (!wp_is_mobile() )
    return;
  
  $cur_url = esc_url((is_ssl() ? "https://" : "http://") . $_SERVER["HTTP_HOST"] . $_SERVER["REQUEST_URI"] );
  if(is_front_page() || is_home() || is_archive()){
    $cur_url .= '?amp=1'; 
  }
  else{
    $cur_url .= 'amp'; 
  }
  // make sure we don't redirect to ourself
  if (function_exists('is_amp_endpoint') && !is_amp_endpoint()) {
    header("Cache-Control: max-age=0, no-cache, no-store, must-revalidate"); //from amclin
    wp_redirect($cur_url);
    exit;
  }
}
add_action('template_redirect', 'wp_ampify_template_redirect');