How to increase PHP memory limit

PHP sets a memory limit on how much PHP script is allowed to use and will exit and throw the following error once the limit is reached;

PHP Fatal error: Allowed memory size of xxxx bytes exhausted (tried to allocate yyyy) in yourscript.php

You'll need to increase the memory limit for PHP scripts to avoid the above error. You can set memory limit for PHP using any of the available methods.

This method will apply to all the PHP scripts that run in the system. It is a good method to follow if you're not hosting multiple systems in a single host.

1. Open PHP configuration file using your preferred text editor.

   $ sudo vi /etc/php/7.2/apache2/php.ini

   Related: PHP configuration files

2. Search for memory_limit directive within the configuration file.

   ; Maximum amount of memory a script may consume (128MB)
   ; http://php.net/memory-limit
   memory_limit = 128MB

3. Set the memory limit value with appropriate unit.

   ; Maximum amount of memory a script may consume (128MB)
   ; http://php.net/memory-limit
   memory_limit = 512MB

4. Restart your web server for the changes to take effect.

   Related: How to start, restart and stop Apache service

To make the setting effective only to a certain folder (or project), you can use the .htaccess file to do the trick. To do this locate (or create) .htaccess file in your PHP scripts folder and add the following line;

php_value memory_limit 512MB

This is probably the best method as the setting applies only to the particular script, and would not allow other poorly written scripts to also consume and waste the system's memory.

To do this, add the following line in your PHP script;

ini_set('memory_limit', '512MB');

You don't have access to PHP's configuration file if you're hosting your system in cPanel, but cPanel do provide the option to change the setting from its admin dashboard.