How to enable exec()

PHP configuration
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_sourcesystem or shell_exec as well, just add them back to the line and save the changes.