<select name="id" id="mySelect" onchange="myFunction()">
                                            <option value=\"0\">Nie wybrano kategorii</option>
<option value=\"1\">Nie wybrano kategorii</option>
<option value=\"2\">Nie wybrano kategorii</option>
<option value=\"3\">Nie wybrano kategorii</option>
<option value=\"3\">Nie wybrano kategorii</option>
                                            
                                        </select>

<?php
                                        db_connect();
                                    ?>
                                    <script type="text/javascript">
                                        function myFunction() {
                                            
                                            var x = document.getElementById("mySelect").value;
                                            $('#images').load('img.php?value=' + x);
                                          
                                        }
                                    </script>
                                    <?php
                                        db_close();
                                    ?>

<div class="col-sm-12">
        <?php
            $id = $_GET['value'];
            $inquiry = mysql_query("SELECT * FROM images WHERE category_id='$id'");

            while ($row = mysql_fetch_row($inquiry)) {
              $category_name = $row[1];
              $img_link = $row[2];
              echo '<div class="col-sm-3"><a href="'. ($img_link) .'" data-lightbox="'. ($name_box[$i]) .'" data-title="'. ($name_box[$i]) .'"><img style="padding: 5px; width: 100%;" src="'. ($img_link) .'" alt=""/></a></div>';
            }
        ?>
    </div>

Warning: mysql_query() [function.mysql-query]: Access denied for user ''@'localhost' (using password: NO) in /home/matti9410/domains/matti9410.unixstorm.org/public_html/admin/img.php on line 5

Warning: mysql_query() [function.mysql-query]: A link to the server could not be established in /home/matti9410/domains/matti9410.unixstorm.org/public_html/admin/img.php on line 5

Warning: mysql_fetch_row() expects parameter 1 to be resource, boolean given in /home/matti9410/domains/matti9410.unixstorm.org/public_html/admin/img.php on line 7