This step by step is to change and manage the php variables in your hosting account, the changes will affect any script running in your hosting account. If you are looking to make changes specifically on certain or one directory to only affect the php scripts running on it, please check THIS tutorial in our knowledgebase about how to manually change php variables in a directory.
1- Login in your cPanel.
2- Go to the "Software" section in the panel and click in the "Select PHP Version" icon/link.
3- Click in the "Switch to PHP options" button. This let you modify many of the php variables in your php.ini for your account. Simply click in the variable current status and you will be able to modify it.