Figure out the default wsl with the command:
`C:\Windows\System32\wslconfig /list`

Windows Subsystem for Linux Distributions:
Ubuntu-18.04 
Legacy (Default)

Set the default to Ubuntu-18.04 (or whatever version you need)
`C:\Windows\System32\wslconfig /setdefault Ubuntu-18.04`

Set the terminal path in PhpStorm settings>tools>terminal to
`C:\Windows\System32\wsl.exe`