Untitled

\this is the admin login///

<?php
session_start();
include '/conn.php';
?>

<head>

        <title>Reservation portal | Admin Login</title>
    <link href="/booking/css/styling.css" rel="stylesheet" type="text/css">
</head>
<body>

    <div class="mobile-screen">
  <div class="header">
    <h1>Log in</h1>
      <h3>Admin</h3>
  </div>

        <ul class="nav">
  <li><a href="/booking/index.php">User</a></li>
  <li><a>Admin</a></li>
</ul>

<!--          <div class="logo"> <img src="images/epic.png" alt="image"/></div>-->

<!--   Log In form     -->
  <form id="login-form" role="form" action="adminLogin.php" method="post">

      <select id="UserName" name="UserName" placeholder="Username" required>
          <option value="" style="background: darkgrey; " ></option>
<?php
          $sqlUser = "SELECT * FROM admin ORDER BY UserName  DESC";
            $radmin = mysql_query($sqlUser);

                while ( ( $rowAdm = mysql_fetch_array($radmin) ) != false ) {
                ?>
                <option style="background-color: rgba(255,255,255,0.3);" value="<?php echo $rowAdm['UserName']; ?>">
                    <?php echo $rowAdm['UserName'];  ?></option>

                        <?php } // close while ?>

</select>
    <input type="password" name="password" placeholder="Password">
    <input type="submit" value="Log In" name="Alogin" class="login-btn button">
  </form>

</div>

</body>

\This is the connection///

    <?php
    // DB credentials.
    define('DB_HOST','localhost');
    define('DB_USER','root');
    define('DB_PASS','');
    define('DB_NAME','reservationdb');
    // Establish database connection.
    try
    {
    $dbh = new PDO("mysql:host=".DB_HOST.";dbname=".DB_NAME,DB_USER, DB_PASS,array(PDO::MYSQL_ATTR_INIT_COMMAND => "SET NAMES 'utf8'"));
    }
    catch (PDOException $e)
    {
    exit("Error: " . $e->getMessage());
    }
    ?>