To enable exec() function, you need to remove it from the following line in your php.ini file:
disable_functions = "show_source, system, shell_exec, exec"
1. Open your php.ini and find the following section:
2. Remove exec from the line and click on Save Changes:
3. If you need to disable show_source, system or shell_exec as well, just add them back to the line and save the changes.
If your account is hosted on a shared server, the suPHP or LSPHP configuration directive should be added to your .htaccess file to make these settings global for the entire account. You can find step-by-step instructions here.
In case your account is located on a business server, no other modifications should be applied.