<?php
if(isset($_POST['listbox']) && !empty($_POST['listbox'])) {
    $servername = "localhost";
    $username = "root";
    $password = "0snata";
    $dbname = "auzvono";

    // Create connection
    $conn = new mysqli($servername, $username, $password, $dbname);
    // Check connection
    if ($conn->connect_error) {
        die("Greska: " . $conn->connect_error);
    }
    $vreme = $_POST['listbox'];
    $query = 'DELETE FROM prof WHERE vreme="'.$vreme.'"';
    if($conn->query($query)) {
        return header('Location: index.php');
    }
}