<!--scripts and css form Jquery date field-->
 <link rel="stylesheet" href="//code.jquery.com/ui/1.11.2/themes/smoothness/jquery-ui.css">
<script src="//code.jquery.com/jquery-1.10.2.js"></script>
<script src="//code.jquery.com/ui/1.11.2/jquery-ui.js"></script>
 <script>
$(function() {
$( "#datepicker" ).datepicker();
});
</script>
<?php

if(!empty($_POST['firstname'] && !empty($_POST['lastname']) && !empty($_POST['dateofbirth']) )) {
        $ime = $_POST['firstname'];
        $prezime = $_POST['lastname'];
        $datumRodjenja=  $_POST['dateofbirth'];
}
?>

<!-- FORM -->
<div class="wrap">
    <?php    echo "<h2>" . __( 'One Crazy Plugin', 'oscimp_trdom' ) . "</h2>"; ?>

    <form name="cool_form" method="post" action="<?php echo str_replace( '%7E', '~', $_SERVER['REQUEST_URI']); ?>">
        <input type="hidden" name="oscimp_hidden" value="Y">
        <?php    echo "<h4>" . __( 'Podaci o studentu: ', 'oscimp_trdom' ) . "</h4>"; ?>
        <p><?php _e("First name: " ); ?><input type="text" name="firstname" value="<?php echo $ime;?>" size="20"></p>
        <p><?php _e("Last name: " ); ?><input type="text" name="lastname" value="<?php echo $prezime; ?>" size="20"></p>
        <p><?php _e("Datum rodjenja: " ); ?><input type="text" name="dateofbirth" id="datepicker" value="<?php echo $datumRodjenja ;?>" size="20"></p>

        <hr />
        <p class="submit">
        <input type="submit" name="Submit" value="<?php _e('Update Options', 'oscimp_trdom' ) ?>" />
        </p>
    </form>
</div>
<?php
global $wpdb;

showresult();


$wpdb->insert(

   'TestTable',
   array(
      'Ime' => $ime,
      'prezime' => $prezime,
      'datum'=>$datumRodjenja
   ),
   array(
      '%s',
      '%s',
      '%s'
   )
  );
$wpdb->print_error();


?>