Comparing Memory Variables

Hi Everyone, I am having a little trouble getting a memory variable and a session variable to compare correctly I have an if statement as below: if ($id=='{$SESSION["id"]}') { echo "working"; } ID is a memory variable that is equal to five, and the session variable id is also equal to five. When I do through the check again $id is set to be the characters {$SESSION["id"]} rather than the five that it was previously assigned to. Basically what it is doing is assigning the characters proceeding the = sign to the variable $id rather than doing the comparison. Does anyone know how I can get around this. I tried two = signs and the working message does not display, but one = sign displays the message but does it also changes the value of $id. Has anyone got any idea how I can get around this problem? Thanks, Michael.