<?php
dateIndaysoff($_GET['date']);
function dateIndaysoff($mydate){
 if(!$mydate)return false;


                $host = "localhost";
                $user = "user";
                $pass = "pass";
                $databaseName = "db";
                $con = new mysqli($host,$user,$pass,$databaseName);
                if ($con->connect_error) {
                    die("Connection failed: " . $conn->connect_error);
                    }

                $query = "SELECT date FROM table WHERE date = '$mydate'";
                $result = $con->query($query);
                 if ($result->num_rows < 1) {$exists =  "FALSE";} else {$exists = "TRUE";}
                 return $exists;
            }
        ?>

jQuery(".datepicker").change(function() {
   var val = jQuery(this).datepicker().val();
   var finalval = jQuery.get("url-to-phpfile/daysoff.php",{date:val});
  if (finalval) {