Using variables within a SELECT statement

I'm working on an application that selects a user's userid if their password and login match. If the login and password match I want my variable $cir to run its own select statement and return its corresponding contactid...for this example we'll say that value = 5. I then want to plug in $cir into my select statement that will show the user the list of his/her contacts and only theirs. This seems to be the select statement that's giving my problems. $query = "select * from my_contacts where contactid=$cir"; Whenever I run my script I get an error saying that I have a problem with my sql syntax. I know that the problem is with the variable becuase it runs fine with a value in it. I've tried writing the $cir as '$cir' and '\$cir' but nothing seems to work. Can anyone help. Thanks in advance Kevin