Update problem bdd!

Hello,
Trying to update my SQL database.
When I use the following query everything works:
mysql_query ( "UPDATE table SET $ login = 'Admin', pass = 'Password' WHERE login = 'Me");

But with the following query, this does not work:
mysql_query ( "UPDATE table SET $ login = '$ login' pass = 'pass' WHERE login =' $ login");

Why ??? !!
Thank you for helping me.

Try this:

mysql_query ( "UPDATE $ table SET login ="'.$ login. '", pass = "pass" WHERE login ="'.$ login .'"');

Thank you,
But your code does not work.
I have the following error:
Parse error: parse error, unexpected T_STRING

So I tried to change it, but the outcome is identical:
mysql_query ( "UPDATE $ table SET login ="".$ login." pass = "" pass "" WHERE login ="".$ login .""');

I understand it ...