Well, if you see below error when using WordPress, which means you need to increase the memory limit for WordPress.
Fatal Error: Allowed memory size of xxxxxx bytes exhausted
As a CMS written using PHP, the memory of WordPress could use in each request is limited by PHP memory_limit. The minimal value to run WordPress smoothly is 32MB, however, if you install a lot of plugins or insert large image in your blog, then you need to increase this value to 64MB or even 128MB.
You could refer to How to Increase PHP Memory Limit to know how to increase it at system level. And in below, we will share some simple ways, via which you only need to modify the configuration of WordPress and then increase PHP memory limit at running time.
Altering PHP Memory Limit via wp-config.php
For this method you won't have to create any extra files in your directory. Add the following code (below) to your wp-config.php file to increase your PHP Memory Limit to 64MB.
Changing PHP Memory Limit via install.php
This way is also very simple, all you need to do is to modify install.php file and place the following code to it:
install.php file is located in wp-admin folder.
Fail to Increase PHP Memory Limit for WordPress
This is possible since your Web Host might limit the maximal PHP memory_limit at system level so that your modification during running time might fail. In this case, contact your web host and ask for the change, or you need to find a new WordPress hosting solution which allows for larger PHP memory limit.