title: shell_exec does not run some shell commands
body: <p>For example, when I try to execute </p>
  
  <pre><code>$output=shell_exec('ls -l');
  echo "&lt;pre&gt;$output&lt;/pre&gt;";
  </code></pre>
  
  <p>It succesfully prints the output of 'ls -l'.</p>
  
  <p>However, I cannot run a shell script which simply creates a file: </p>
  
  <pre><code>shell_exec('sh /home/ubuntu/Desktop/myScript.sh');
  </code></pre>
  
  <p>Is it about user access permissions defined in apache?</p>
  
  <p>How can I fix it?</p>