PHP SQL Not updating row in database - php

Question

I'm currently making a simple script that takes a user input named comments and putting it in a database. Every time I use the same email, I want it to overwrite their last entry. However, it keeps putting a new entry every time. Here is my code:
if($comments){
try{
echo "<img width=\"245\" height=\"130\" src=\"logo.png\"/><br/>";
echo "<h1>Thank you. You should receive your order on xx-xx-xx</h1>";
$TF = "TRUE";
if($numrows == 0){
$postquery = "INSERT INTO TTT25 (email,card,changes,comments) VALUES ('$email','$businesscard','$TF','$comments')";
$querythepost = sqlsrv_query($conn, $postquery);
}
else{
$postquery = "UPDATE TTT25 SET changes = '$TF', comments = '$comments' WHERE email = '$email'";
$querythepost = sqlsrv_query($conn, $postquery);
}
}
catch(Exception $e){}
}
elseif($optout=="false"){
echo "<img width=\"245\" height=\"130\" src=\"logo.png\"/><br/>";
echo "<h1>Thank you. You should receive your order on xx-xx-xx</h1>";
$TF = "FALSE";
$comments = "";
if($numrows == 0){
$postquery = "INSERT INTO TTT25 (email,card,changes,comments) VALUES ('$email','$businesscard','$TF','$comments')";
$querythepost = sqlsrv_query($conn, $postquery);
}
else{
$postquery = "UPDATE TTT25 SET changes = '$TF', comments = '$comments' WHERE email = '$email'";
$querythepost = sqlsrv_query($conn, $postquery);
}
}
Sorry it must have cut off:
my num rows and other variables defined before the conditional statements:
$optout = $_GET['opt'];
$encodedemail = $_GET['email'];
$email = base64_decode($encodedemail);
$originalcard = base64_decode($_GET['card']);
$businesscard = $originalcard;
$comments = $_POST['comments'];
//$primary = md5(uniqid(rand (), true)); no longer needed
$postquery;
$TF;
$sqlmatch = sqlsrv_query("SELECT * FROM TTT25 WHERE email = '".$email."'");
$numrows = sqlsrv_num_rows($sqlmatch);
echo $numrows;