I think the OP is trying to insert the day into the database. If that isn't what you want, try being a bit more clear. Otherwise, to insert the day that the script was executed by the user, try this:
1-Define today
Code:
$today = date("l");
2-Insert this into the db
Code:
//your db connection goes here
$query=mysql_query("INSERT into TABLE (theday) values ('$today')");