Anyone working with WordPress (or any other PHP based system) had a chance to see one of the most common fatal errors PHP has to offer: Allowed memory exhausted. This is easy to fix, and depending on your host and personal preference, there are several methods to do it.
Older WordPress versions (before 2.9) could work with 16M of PHP memory. Even later 3.x versions can work with so little memory if you don’t use any plugins. But, using plugins increases memory requirements, and using the only 32M is at most times, not enough. For latest WordPress with an average of 20 plugins, you will need 48M to 64M. Most hosting companies keep this value at 32M, so when you upgrade WordPress, upgrade plugin or add new plugins, you will run out of memory and you will see variation of this error (on screen or in log, depending on server settings):
Fatal error: Allowed memory size of 33554432 bytes exhausted (tried to allocate 345234 bytes) in /path/to/public_html/wp-content/plugins/plugin.php on line 56.
To increase memory, you can use different methods. Examples bellow are for 64MB of memory. You can set it lower and experiment with higher values. Setting this to 128M or 256M is fine also, PHP will really use as needed, this value is a limit. Use only one of these methods, don’t use all of them at the same time!
Method 1: Change PHP.ini
On some shared hosting servers and on VPS or other dedicated hostings, you will have access to the php.ini file with all main PHP settings. This file should have memory directive, so you need to find it and change it, if it is not there, you need to add it. Here is the directive you need to find/add and set different value for memory size:
memory_limit = 64M
Method 2: Use .htaccess
If you don’t have access to php.ini, the same thing can be done using .htaccess file. This file is in the root folder of your website, if it’s not there you can add it, but in most cases, it is added by WordPress. This file is only available on Apache servers. Again, search for this in that file, if it is not there add it, and set memory value you need:
php_value memory_limit 64M
Method 3: Use WordPress wp-config.php
WordPress way to do this is using the almighty wp-config.php file. If this define is in the file, change it to memory value you want, if it’s not there add it before “That’s all, stop editing!” comment in that file. Here is the code to find and change or add if not there.
Method 4: Contact your hosting company
If you don’t want to do it on your own, you can always contact your hosting company support. Some hosting companies can impose a limit to this value, so whatever you try to change it will fail, and only hosting support can change it for you (if they want to). If you can’t change memory limit, it is time to find some better hosting that will allow you to do so.