title: Get window size with php
body: <p>What is the problem this code:</p>
  
  <pre><code>$window_width= '&lt;script&gt;screen.availWidth&lt;/script&gt;';
  $window_height= '&lt;script&gt;screen.availHeight&lt;/script&gt;';
  </code></pre>
  
  <p>any idea?</p>