title: Get and update usermeta in wordpress onclick
body: <p>I try to make a feature to my website. When the user presses a link leads it to a PHP file. in the URL is a request, like this: </p>
  
  <pre><code>    &lt;a href="'. plugins_url() .'/gps_konkurranse/gps_konkurranse.phpfunnet=true&amp;user_ID='. $user_ID .'" target="_blank"&gt;
  </code></pre>
  
  <p>in the file opened must run a php function that retrieves existing user meta, adds 1 and updates the same user meta.</p>
  
  <p>This is the code I have so far. Can someone help me</p>
  
  <pre><code>    &lt;?php
      if($_GET['funnet'] == 'true'){
          $funn = get_user_meta($_GET['user_ID'], 'gps_funn', true );
          $funn++
          update_user_meta( $_GET['user_ID'], 'gps_funn', $funn );
  
      }
  
      ?&gt;
  </code></pre>
  
  <p>this code is in a standalone php file</p>