PHP - how to make MySQL select query with MySQL?

<?php

​

    if(isset($_GET['role']))

    {

        $role = $_GET['role'];

​

        $db_name = 'test';

        $db_host = '127.0.0.1'; // 'localhost'

        $db_username = 'root';

        $db_password = 'root';

​

        $mysqli = new mysqli($db_host, $db_username, $db_password, $db_name);

        if($mysqli->connect_error)

            die('Database connection error!');

        if($statement = $mysqli->prepare('SELECT * FROM `users` WHERE `role` = ?'))

        {

            $statement->bind_param('s', $role); // string parameter

            if($statement->execute())

            {

                $statement->bind_result($row_id, $row_name, $row_role);

                echo '<pre>';

                echo "[ID]\t[name]\t[role]<br />";

​

                while ($statement->fetch())

                    echo $row_id . "\t" . $row_name . "\t" . $row_role . '<br />';

                echo '</pre>';

            }

            else

                echo 'Query execution error!';

            $statement->close();

        }

        else

            echo 'Query preparation error!';

        $mysqli->close();

    }

​

?>

CREATE TABLE `users` (

    `id` INT(10) UNSIGNED NOT NULL AUTO_INCREMENT,

    `name` VARCHAR(100) NOT NULL,

    `role` VARCHAR(15) NOT NULL,

    PRIMARY KEY (`id`)

)

ENGINE=InnoDB;

INSERT INTO `users`

    (`name`, `role`)

VALUES

    ('John', 'admin'),

    ('Chris', 'moderator'),

    ('Kate', 'user'),

    ('Denis', 'moderator');