General

When asking this question most users forget that their web server is a multi-user system.

The configuration for the memory_limit of PHP running as an Apache module to server webpages has to take into consideration how many Apache process you can have at the same time on the machine (this is controlled the MaxClients configuration option for Apache).

If MaxClients is 100 and you have 2,000 MB or RAM, a very quick calculation will show that you should not use more than 20 MB *(because 20 MB * 100 clients = 2 GB or RAM, ie the total amount of memory your server has)* for the memory_limit value.

Add to this other software running on the server, like MySQL, mail servers, the operating system and Apache itself and you can easily run out of memory and have odd results.

Joomla

When using the Joomla CMS memory usage can increase dramatically with a large number of extensions installed and a large amount of data to be managed.

Signs that you may be experiencing memory limit problems include

• pages not rendering completely
• components or extensions reporting memory errors
• partial content being returned and
• page timeouts on pages that use a lot of components/extensions.