You shouldn’t need to do this since that’s the default in development: https://github.com/roots/trellis/blob/68cbc413587265c4b9500ea68563923185d64afe/group_vars/development/php.yml#L7-L9
Tangent: reminder to customize variables in group_vars instead of changing role default variables as well 
Not sure if you saw https://discourse.roots.io/t/phpstorm-and-trellis/9962 but it might help.