title: Put JavaScript variable value as the argument of PHP function
body: <p>I have this function in my PHP code.</p>
  
  <pre><code>&lt;?php
   $user = get_user_by_id($user_id);
  ?&gt;
  </code></pre>
  
  <p>And I also have a JavaScript code on the same page. 
  The JavaScript generates some value to a JS variable.</p>
  
  <p>What I need to do is, using that JavaScript variable value as the argument of the above PHP function.</p>
  
  <p>So, what's the simplest method for achieving this..?  </p>