$date1 = $_REQUEST['date_1'];
    $date2 = $_REQUEST['date_2'];

    //Remove the "/"s in the date, as this confuses the function which creates the DateTime object
    $date1 = str_replace("/", "-",$date1);
    $date2 = str_replace("/", "-",$date2);

    // convert these date strings to the DateTime object for manipulation
    $date1 = date_create($date1);
    $date2 = date_create($date2);


    // Convert these DateTime objects to show the date in a differnt format as a string
    $date1 = date_format($date1, "Y-m-d");
    $date2 = date_format($date2, "Y-m-d");