Where phpstorm indexes located? And how to change location path?
Adjust the settings in this file: 

IDE_HOME\bin\idea.properties


Change these options: 


idea.config.path 
idea.system.path 
idea.plugins.path 
idea.log.path


My Source:
https://intellij-support.jetbrains.com/hc/en-us/articles/206827407-Changing-IDE-
default-directories-used-for-config-plugins-and-caches-storage

Here is some additional information:
https://intellij-support.jetbrains.com/hc/en-us/articles/206827437-Directories-used-by-the-IDE-to-store-settings-caches-plugins-and-logs