Fallback Javascript with PHP from CDN to Local Storage on Unavailable -

i need help. create fallback sourcecode. using cdn host javascript , css , images. trying create fallback in php instance ip 123.456.789 not available in 400ms php falback fetch local storage @ 987.654.321

so thinking on lines of (bare me, amatuer example)

if ip 123.456.789 in 400ms   //show file 123.456.789  else  //show file 987.654.321 

i have source code hard coded such as:

<script type="text/javascript" src="123.456.789/js/jquery.js"></script> 

so if 123.456.789 not available in 400ms 1 load

<script type="text/javascript" src="987.654.321/js/jquery.js"></script> 

i answered own question while ago. decided share here.

<?php //debug off default error_reporting(0);  //cdn fallback if (!isset($_get['aws_cdn'])) {          $cdn_fallback = curl_init('http://123.456.789/'); //set cdn ip or url         curl_setopt($cdn_fallback, curlopt_returntransfer, true);         curl_setopt($cdn_fallback, curlopt_nosignal, 1);         curl_setopt($cdn_fallback, curlopt_timeout_ms, 400); //how many milliseconds before fallback local storage          $data = curl_exec($cdn_fallback);         $curl_errno = curl_errno($cdn_fallback);         $curl_error = curl_error($cdn_fallback);         curl_close($cdn_fallback);          if ($curl_errno > 0) { ?>       <script type="text/javascript" src="http://example.com/js/jquery.js"></script>       <?php } else { ?>     <script type="text/javascript" src="http://123.456.789/cdn/js/jquery.js"></script>       <?php }} ?>