title: PHP can't execute shell from browser
body: <p>I'm following <a href="http://code.tutsplus.com/tutorials/the-perfect-workflow-with-git-github-and-ssh--net-19564" rel="nofollow">this tutorial</a>. </p>
  
  <p>I cannot get the <code>gitpull.php</code> script to execute a git pull when accessing the script through the browser. </p>
  
  <p>I can manually execute a <code>git pull</code> from shell on my remote server. </p>
  
  <p>I can manually run the php script: </p>
  
  <pre><code>&lt;?php `git pull`; 
  </code></pre>
  
  <p>which uses back ticks to run shell if I explicitly call the script in shell. <code>php gitpull.php</code></p>
  
  <p>I've checked permissions on the php file and the file belongs to <code>www-data</code> user. Why can I run the script through the shell but not the browser? </p>