A small php task

Hello , i have this .htaccess rule : RewriteRule ^([^_]*)_([^_]*)\.html$ /[login to view URL]$1&device_id=$2 [L] now the problem is that it does not put a - in the space ... for example : it is generating this url: [login to view URL] ... i want to replace %20 with a - sign. The person who sends me the correct rule earns 2 dollars.