If Then Syntax ??

echo $_SESSION["UserID"];
if ($_SESSION["UserID"] = "johnsmith")

{

// header("location: http://www.google.com";);

// exit();

echo $_SESSION["UserID"];

}
==========================================================================

Line 1 echos the CORRECT Login User id

Line 2 is supposed to test for that user ID and do something for a particular user,

but it is really just setting the userid to Johnsmith" rather than testing for it
Can you give me some direction ???