Please Help in PHP Problem

[narensen]

Hello everybody i am new to PHP and trying to learn more and more. now i am trying to make a reservation system i solved my date time problem but now i am stick on comparing two date from my form with two dates on my database here is my code and query :

form:
There is two textboxes one is Checkin and second is Checkout which i want to compare with stored dates in database.
And for that i am using following php code in same at the top:

if (isset($_POST['submit'])) {


$dt = date('yyyy-mm-dd', strtotime($_POST['Checkin']));
$dt1 = date('yyyy-mm-dd', strtotime($_POST['checkout']));
        $errors = array();

        // perform validations on the form data
        $required_fields = array('Checkin', 'checkout');
        $errors = array_merge($errors, check_required_fields($required_fields, $_POST));

        $Chkin = trim(mysql_prep($_POST['Checkin']));
        $Chkout = trim(mysql_prep($_POST['checkout']));


        if ( empty($errors) ) {

$query = "SELECT checkin, checkout ";
            $query .= "FROM bookd ";
            $query .= "WHERE checkin BETWEEN $Chkin and $Chkout ";
            $query .= "AND checkout BETWEEN $Chkout and $Chkout";
            $result_set = mysql_query($query);
            confirm_query($result_set);
            if (mysql_num_rows($result_set) == 1){
                $message = "Not avilable";
                }

                else{
                    $message = "avilable";
                    }
}
}
?>

So please tell me what should i do or there is any other way to get this happen. But please give me reply in brief because i am new to this language.