Untitled

<!DOCTYPE html>
<html>
<head>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11/jquery.min.js">
</script>

<script>
$(document).ready(function() {

    //the min chars for promo-code
    var min_chars = 6;

    //result texts
    var checking_html = 'Checking...';

    //when keyup
    $('#code').keyup(function(event){
        //run the character number check
        if($('#code').val().length == min_chars){

            //show the checking_text and run the function to check
            $('#Promo_code_status').html(checking_html);
            check_code();
        }
    });

});

//function to check the promo code
function check_code(){

    //get code
    var code = $('#code').val();

    //use ajax to run the check
    $.post("check_code.php", { code: code },
        function(result){

        //if the result is 0
        if(result == 0){
            //show that the code is correct
            $('#Promo_code_status').html(code + ' is correct.');
        }else if(result == 1){
            //show that the code is correct, but already has been used
            $('#Promo_code_status').html(code + ' has allready been used.');
        }else{
            //show that the code is not correct
            $('#Promo_code_status').html(code + ' is not correct.');
        }
    });
}
</script>
</head>
<body>

<center><h1>Enter Promo Code</h1>
<form method="post" action="check_code.php">
    <input type="text" id="code" name="code" maxlength="6" />
    <div id="promo_code_status"></div>
    <br>
    <input type="submit" value="Let's go"></center>

</form>

</body>
</html>

<?php

//connect to database
$user = "***";  //Username
$pass = "***";  //Password
$host = "localhost";  //Host
$dbdb = "***";  //Database name

$connect = mysqli_connect($host, $user, $pass, $dbdb);
if(!$connect)
{
trigger_error('Error connection to database: '.mysqli_connect_error());
}

//get the code
mysqli_real_escape_string($connect, $_POST['code']);

//mysql query to select field code if it's equal to the code that we checked '
$result = mysqli_query($connect, 'select Code from Codes where Code = "'. $code .'"');
$record = mysqli_fetch_array($result);

//if number of rows fields is bigger them 0 that means the code in the database'
if(mysqli_num_rows($result) > 0){
 if($record['used'] == 0) {
     //and we send 0 to the ajax request
     echo 0;
} else{
    //and we send 1 to the ajax request
    echo 1;
}
}else{
//else if it's not bigger then 0, then the code is not in the DB'
//and we send 2 to the ajax request
echo 2;
}
?>

$code = mysqli_real_escape_string($connect, $_POST['code']);