New-SpSite cmdlet with parameters list

Hi everyone !

In a PS script on a Sharepoint server, I'm trying to call a cmdlet with some arguments.

This is OK :

New-SpSite -url $url -owneralias $owneralias

However, I have the requirement to create a parameter list with arguments that sometimes are present, sometimes not. So I thought it was possible to create a string like this $Paramlist = "-url "+$url+" -owneralias "+$owneralias ... But It's not ok, PS give me various errors.

What is the best method to construct a parameters list ?

TY for your assistance. Have a nice day.

J.