shell_exec() has been disabled for security reasons
1. SSH to the server
2. Edit the php.ini file (on cpanel it’s /usr/local/lib/php.ini)
3. Search for the line that says “disable_functions”
4. Remove shell_exec from this line
5. Save the file, and restart apache.
NOTE: If you do not have root access to the server, then you’ll need to ask your hosting provider to do this for you.