How do i do so, when the first select has not been defined yet, the secound one will be deactivated?

Im wondering is it possible in php, to do when the first select has a value the next one will be activated, like having the secound one called album SELECTOR grayed out untill the category SELECTOR has been defined?

<?php
            //CATEGORY SELECTOR
            $sql = "SELECT * FROM category ORDER BY cat_id"; 
            $result = $mysqli->query($sql);

                echo "<select class='input' name='photo_category'>";
                echo "<option disabled selected>Choose a category</option>";

                            while ($row = $result->fetch_array(MYSQLI_ASSOC)) {

                                echo "<option value='$row[cat_id]'>$row[cat_title]</option>";
                            }

                echo "</select>";

            //ALBUM SELECTOR
            $sql = "SELECT * FROM albums WHERE album_type = 0 ORDER BY album_id"; 
            $result = $mysqli->query($sql);

                echo "<select class='input' name='photo_album'>";
                echo "<option disabled selected>Choose an album</option>";

                            while ($row = $result->fetch_array(MYSQLI_ASSOC)) {
                                echo "<option value='$row[album_id]'>$row[album_title]</option>";
                            }

                echo "</select>";
    ?>