rocknbil - 4:33 pm on Nov 8, 2011 (gmt 0)

$id=$_POST['id']; // is showing up in the address bar

Then . . . your form is still submitting as GET. Post variables won't show up in the address bar.

add these two at the end.

echo "<p>POST</p>";
var_dump($_POST);
echo "<p>GET</p>";
var_dump($_GET);

that should tell you what's actually being submitted.

the data is alphanumeric and has both upper and lowercase as well

OK, well make sure it's got an index on the column. :-) You might make sure the user id is stripped of beginning/ending whitespaces before insertion.