When I install PhpStorm from JetBrains Toolbox app I do not have an option to open folders as project when right clicking
Sadly JetBrains Toolbox App does not provide such functionality. Only standalone installer has an option to make them right now. You will have to either use that... or create such entries manually.
https://youtrack.jetbrains.com/issue/TBX-2478 -- watch this ticket (star/vote/comment) to get notified with any progress.
To add an entry to the Windows Explorer's right-click menu:
.bat
file: https://youtrack.jetbrains.com/issue/IDEA-114307#comment=27-2125363 (at very least it lists Registry keys where to create such an entry).