You need to increase PHP Memory limit when you are Working with a large Theme like Marketplace Theme, Directory Theme. I don't mean that you need to increase PHP memory limit in any Marketplace or Directory Theme but sometimes it needs to increase is a simple Theme too. It depends on Theme configuration and you server configuration.
It can be done with a plugin if you have permission to edit WordPress files from the Dashboard. This can be done with a plugin.
Increase PHP Memory Limit Via WordPress Cpanel
Navigate to your root folder and search for wp-config.php file. Open this file via your cpanel editor and you will see something like the following screenshot.
Now just paste the following code inside your wp-config.php file.
/** Memory Limit */
This is the easy method for increasing PHP memory limit.
But, if you don't have permission for customizing config file from the Dashboard then you should follow the second step.
Increase Memory Limit Via FTP:
This is easy then Dashboard. Just need to put a code in your wp-config.php file. Copy the following code and paste it on your config file.
/** Memory Limit */ define('WP_MEMORY_LIMIT', '256M');
If you have still problem with it then you can watch the following video. I have showed you details and step by step guide for increasing PHP memory Limit in a WordPress Website.
Let's Wrap Up!!!
I hope you have solved your Memory Limit problem. If you follow the Dashboard system then you may face problem sometimes with your server configuration. I recommend you to work with FTP and mind that what you are changing in your file. Though you work on dashboard please access your FTP for security. If you have done something wrong in Dashboard then you can fix it via FTP.