How can one troubleshoot and resolve the PHP Fatal error: Allowed memory size issue?

The PHP Fatal error: Allowed memory size issue occurs when a PHP script tries to allocate more memory than the limit set in the php.ini file. To resolve this issue, you can increase the memory_limit value in the php.ini file or by adding ini_set('memory_limit', '256M'); in your PHP script.

ini_set('memory_limit', '256M');