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 or more is fine also, PHP will really use as needed, this value is the limit. Use only one of these methods, don’t use all of them in 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 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, 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 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 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.