Register

<?php
   include('config.php');
if($_SERVER["REQUEST_METHOD"]== "POST"){
    $myusername = mysqli_real_escape_string($db,$_POST['username']);
    $mypassword = mysqli_real_escape_string($db,$_POST['password']);
    $myemail = mysqli_real_escape_string($db,$_POST['email']);

    $validation = "SELECT username FROM carpool_ WHERE username = '$myusername'";
    $validResult = mysqli_query($db,$validation);
    $validCount = mysqli_num_rows($validResult);

    if ($validCount != 1){
    $sql = "INSERT INTO carpool_ (username, password, email) VALUES ('$myusername', '$mypassword' , '$myemail' )";
      $result = mysqli_query($db,$sql);
    }else{
        $duplicate =  "This username is already installed";
    }


}
?>
<html>

   <head>
      <title>Register</title>
        <style type = "text/css">
         body {
            font-family:Arial, Helvetica, sans-serif;
            font-size:14px;
         }

         label {
            font-weight:bold;
            width:100px;
            font-size:14px;
         }

         .box {
            border:#666666 solid 1px;
         }
      </style>
   </head>
    <body bgcolor = "#FFFFFF">

      <div align = "center">
         <div style = "width:300px; border: solid 1px #333333; " align = "left">
            <div style = "background-color:#333333; color:#FFFFFF; padding:3px;"><b>Register</b></div>

            <div style = "margin:30px">

               <form action = "" method = "post">
                  <label>Username  :</label><br /><input type = "text" name = "username" class = "box" required/><br /><br />
                  <label>Password  :</label><br /><input type = "password" name = "password" class = "box" pattern=".{8,16}" required title="8 to 16 characters"/><br/><br />
                   <label>Email  :</label><br /><input type = "email" name = "email" class = "box" required/><br/><br />

                  <input type = "submit" value = " Register   "/><br />
               </form>

               <div style = "font-size:11px; color:#cc0000; margin-top:10px"></div>

            </div>

         </div>

      </div>

   </body>

</html>