By default, the PHP memory limit is set at 128MB. This is sufficient for most websites. However, if your application displays a fatal memory error, you will need to increase the PHP memory limit.
To do so login your cPanel. Under the Software heading, click on MultiPHP INI Editor.
Once you click on it a new screen will load and it will allow you to
manage your custom php.ini using the Basic Mode or Editor Mode. The
Basic mode includes part of the PHP directives. Those are the most
frequently used and modified by customers. If a php option is not present in the basic mode editor then you need to use the Editor Mode.