Extracting data from a column using mysqli::bind_result() - php

Question

My query returns with null in my php code , but when I enter the same query into phpmyadmin it returns the row to which it belongs. Here is the database I am using
CREATE TABLE `payment`.`users`(
`u_id` int(12) NOT NULL AUTO_INCREMENT,
`email` varchar(255) NOT NULL,
`passwd` varchar(100) NOT NULL,
PRIMARY KEY (`id`),
UNIQUE KEY (`email`)
) ENGINE=MyISAM;
and here is the code i am using that is returning null when it clearly works in phpmyadmin.
function getUserId($email, $passwd) {
$mysqli = db_connect();
$query = "SELECT `u_id` FROM `payment`.`users` WHERE `email`='$email' AND `passwd`='$passwd' ORDER BY 1";
if ($stmt = $mysqli->prepare($query)) {
/* execute query */
$stmt->execute();
$stmt->bind_result($u_id);
while ($stmt->fetch()) {
return $u_id;
}
}
}

Answer 1

The thing is that you are using variables in your php code to set the values. In phpMyAdmin you're inserting values directly, therefore the problem may be in the values inserted.
First of all use PDO's bindParam() or mysqli's bind_param() statements as they sanitize inputs and help you avoid SQL Injections.
Second good thing about using prepared statements and binding params is that you can specify the type of the data being binded to to the query which in most cases will fix such problems. Though in your case you're probably inserting strings.