title: PHP Notice: Undefined variable:
body: <p>i try to run a command in server from php
  so i added this code in a php file </p>
  
  <pre><code> shell_exec($cmd);  
  
   echo $cmd = "at ".$_POST['time1']." &lt;&lt;&lt; '/usr/local/bin/youtube-dl  ".$_POST['url']." -o ".$out." &amp;&amp; /root/bin/ffmpeg -y -i ".$out." -c:v libx264 -s 640x360 -b:v 300k -strict experimental -movflags +faststart -c:a aac FILMA/".$out."___www.example.com___.mp4 &amp;&amp; rm -f ".$out."'";
  </code></pre>
  
  <p>When i run it i get this error</p>
  
  <blockquote>
    <p>PHP Notice:  Undefined variable: cmd in /var/www/html/1.php on line __, referer: <a href="http://example.com/1.php" rel="nofollow">http://example.com/1.php</a></p>
  </blockquote>