PHP (MySQL) error : "Warning: mysql_num_rows() expects parameter 1 to be resource"

Question

if (!empty($_POST)){

    $email_to=$_POST['email_to'];
    $email_to=mysql_real_escape_string($_POST['email_to']);

    $sql = "UPDATE `cosmos`.`members` SET `conf` = '2' WHERE `members`.`email` = '$email_to';";
    $result=mysql_query($sql) or trigger_error(mysql_error().$sql);

    $count=mysql_affected_rows($result);                  // line 20
    if($count==1){

    $rows=mysql_fetch_array($result);
    $unique=$rows['u_code'];
    $name=$rows['username'];
    // ---------------- SEND MAIL FORM ---------------- 
    $to=$email_to; 
    $subject="Your Account Password Request! - Cosmos"; 
    $header="from: Tayal's/Cosmos <[email protected]>"; 
    $messages= "Hey $name ,\r\n";
    $messages.="You recently requested a new password";
    $messages.="<br /><a href='confirm.php?uid" . $unique . "'>Confirmation Link</a> \r\n";
    $sentmail = mail($to,$subject,$messages,$header); 
    echo $messages; 
    }   else {
    echo "Not found your email in our database";
    }


}

Warning: mysql_affected_rows() expects parameter 1 to be resource, boolean given in C:\wamp\www\a\l\forget.php on line 20

Answer 1

$result=mysql_query($sql);

to

$result=mysql_query($sql) or trigger_error(mysql_error().$sql);

and run it again

and then

$email_to=$_POST['email_to'];

to

$email_to=mysql_real_escape_string($_POST['email_to']);

oh yes, and there is also quotes

Answer 2

The SQL you performed was not a SELECT, so no rows are returned!

Answer 3

$result is false because your query is invalid (has a syntax error). Use:

$sql = "UPDATE members SET conf=2 WHERE email = '$email_to';"

(note the quotes surrounding $email_to)

Also mysql_num_rows() should be used for SELECT queries only. For UPDATE, INSERT and DELETE, use mysql_affected_rows() instead.

Finally, for future reference, if your query doesn't work, print the error and the SQL query used (something like what's on Col Shrapnel's answer). It will help you know what's wrong.