mysql行计数查询不起作用

Question

I think my problem is in the MySQL sections of my code I need it to count at least one table row to be true and continue the if statement otherwise do the else statement. When I run the code it does not display an error just a blank page besides the username and password echo at the top of the page I was just checking to see if they were passing and they are. My code is below:

<?php

$myusername=$_POST['userName']; 
$mypassword=$_POST['password']; 

echo $mypassword;
echo "<br>" . $myusername;

$myusername = stripslashes($myusername);
$mypassword = stripslashes($mypassword);
$myusername = mysql_real_escape_string($myusername);
$mypassword = mysql_real_escape_string($mypassword);

try {
    $conn = new PDO('mysql:host=localhost;dbname=timecard', 'username', 'password');
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    $stmt = $conn->prepare('SELECT COUNT(*) FROM employees WHERE `userName`= :userName AND `password`= :password');

    $stmt->execute(array(':userName' => $myusername, ':password' => $mypassword));

    } catch(PDOException $e){
        echo'ERROR: ' . $e->getMessage();
    }

$res = $conn->query($stmt);

if($res->fetchColumn() > 0){


session_register("myusername");
session_register("mypassword"); 
header("location:login_success.php");
}
else {
echo "Wrong Username or Password";
}
?>

Answer 1

There is something worng in the way you manage PDO Statements (see doc http://php.net/manual/en/pdostatement.fetchcolumn.php). Delete the line containing :

$res = $conn->query($stmt);

and replace :

if($res->fetchColumn() > 0){

by :

if ($stmt->fetchColumn() > 0) {