mysql_num_rows problem

[wanted420]

This is the code:

$user = $_POST['username'];
$check_user = "SELECT username FROM members WHERE username = $user";
$result_user = mysql_query($check_user);
$num_rows_user = mysql_num_rows($result_user);

This is the problem:

Warning: mysql_num_rows(): supplied argument is not a valid MySQL result resource in C:\Program Files\Apache Group\Apache2\htdocs\register.php on line 76

I do not know what i am doing wrong to get this warning.

[drawmack]

Your query isn't executing successfully try this instead:

$user = $_POST['username'];
$check_user = "SELECT username FROM members WHERE username = $user";
$result_user = mysql_query($check_user);
if($result_user) {
    $num_rows_user = mysql_num_rows($result_user);
} else {
    die($check_user . "<br>" . mysql_errno() . ": " . mysql_error());
}

That will echo out the query and tell you why i'ts failing.

[TheDefender]

Change the query to:

$user = $_POST['username'];
echo $user; // Also echo your $user variable to make sure it is set
$check_user = "SELECT username FROM members WHERE username = '$user'"; 

Then obviously, make sure your user name exists...