Submit form with multiple conditions not working

Situation

I have a submit form. With this form, users are able to reserve a table in a restaurant. Which each submit there is data send to the database with the wp_insert_post function. For example the user_ip and the datum_nieuwe_reservering(explained later). I want to use this to check if the user is allowed to submit a new reservation(prevent spamming). I have tried a couple of thing, but it's not working. See code below.

Question

How can I get this to work? What am I doing wrong?

CODE
reserving.php

    <!-- CODE WHEN POST = SUBMIT, MAKE A NEW RESERVATION.
    =========================================== -->
    <?php
    global $wpdb;
    $user_ip_db = getUserIP();
    $date = date("d-m-Y H:i:s");

    //echo $date;

    $check_user_ip = $wpdb->get_results("SELECT meta_value FROM $wpdb->postmeta WHERE meta_key = 'user_ip_reservering' AND meta_value = '$user_ip_db'");
    $check_time_new = $wpdb->get_results("SELECT meta_value FROM $wpdb->postmeta WHERE meta_key = 'datum_nieuwe_reservering'");

    print_r($check_time_new);


    if ( isset($_POST['submit_reservering']) ) {
      if  ( (empty($check_user_ip)) && $date > $check_time_new ) {
          create_reservering();
          echo "Your reservation has been send";
        } else {
        echo 'You have already reserved';
      }
    }

     ?><!-- end CODE FOR MAKING RESERVATION-->

Plugin file

//Using this function to send the current day + 1 day to the database
//with a hidden text field named `datum_nieuwe_reservering`(show below)
//and in the end check if current date >= `datum_nieuwe_reservering`
<?php
 function getDateTime(){
 date_default_timezone_set('Europe/Amsterdam');
 $next_day = time() + (1 * 24 * 60 * 60);
 $date_now = date('d-m-Y H:i:s');
 $date_tomorrow = date('d-m-Y H:i:s', $next_day);

 echo $date_tomorrow;
}
?>

Hidden field for datum_nieuwe_reservering

 <input type='hidden' value='<?php echo getDateTime(); ?>' name='datum_nieuwe_reservering'>

NOTE: The submit form is working correctly with the if (empty($check_user_ip)) { }; code only. So I'm struggle to add the date in the if statement too.

I hope someone can help me in the right direction!
Thanks in advance.