Everything was broken when we tried to install yet another WP cache plugin. All the tabs and pages from admin panel are showing advanced-cache.php already exists warning.

Warning!
The file ../../wp-content/advanced-cache.php already exists. Please manually delete it before using this plugin.

Origin

Most of the wordpress installation done from dreamhost will have wp super cache plugin installed. This plugin will speed up wordpress blog, and so is recommended. If you do not have cache plugin installed then your wordpress blog will eat up lot of RAM(memory). There are multiple cache plugins available. We were trying out different plugins other than wp super cache. We tried to install hyper cache. Other than hyper cache there are tons of cache plugins, like, wp rocket, w3 total cache, WP fastest cache, Hummingbird page cache, & PageSpeed Ninja and so on.

Well, If you try to install another cache plugin without fist disabling current plugin then you will start to see this warning.

Solution for advanced-cache.php already exists warning

There are multiple solutions available for this warning. Like do FTP or ssh login to your server and remove folder from ‘plugins’ directory. or manually copy the file from the plugin folder ‘wp-content/plugins/wp-super-cache/advanced-cache.php’ to ‘wp-content folder’. And last one suggested to define ‘WP_CACHE’ constant to ‘false’ in ‘wp-config.php’. But none of the solution worked out in our case.

So, we have to do it hard way by editing database table. Login to dreamhost panel, navigate to ‘more’->’MySQL Database’ Click on phpMyadmin link in front of your database. Please note your database username and password will be different from your wordpress credentials. Login to your database and select ‘wp_3cajzx_options’ table. Search for ‘active_plugins’ in option_name as shown in below image.

Under ‘option_value’ you can see that, WP Super cache and Hyper Cache entries are there. First delete ‘hyper cache’ entry and re-order the indexing for ‘i’.

i:5;s:20:"wp-super-cache/plugin.php";i:6;s:22:"hyper-cache/plugin.php";i:7;s:19:"jetpack/jetpack.php";

Corrected entry after removing hyper cache will look like as below.

i:5;s:20:"wp-super-cache/plugin.php";i:6;s:19:"jetpack/jetpack.php";

After doing this change click on ‘go’ with ‘save’ option for this table. This will save the plugins table with removed entry for hyper cache plugin.

With this trick our admin panel is working, and we could see that all the plugins are available, only change was all the plugins were deactivated so we have to activate them. Hope this trick will solve your problem with this warning.