php variables in a backtick command

I am trying to run a shell command with backticks. However, I get a parse error. Is it because I have an array variable in there? $result = `adduser -l=$dist_id -p=$user['password'] --f="$user['name_first'] $user['name_last']"`; Do I need to assign the value to a regular variable before I put it in there? Like this? $pword=$user['password'] $fname =$user['name_first'] $lname =$user['name_last'] $result = adduser -l=$dist_id -p=$pword --f="$fname $lname"; Thanks, Jonathan