<?php
        $query = "SELECT * FROM slider"; // remove LIMIT 1 to select all rows

        $result = mysqli_query($conect_phpmyadmin, $query);
        // $conect_phpmyadmin is bad name as you are not connecting to phpmyadmin but mysql instead
        $i = 0; // set init value as 0
        while ($row = mysqli_fetch_array($result)) {
                $id = $rs['id'];
                $imagem = "../uploads/".$row['desc_img'];
                $active = ($i == 0) ? active : ''; // to set the first slide as active
?>
        <div class="item <?= $active; ?>">
            <img src="<?php echo $imagem ?>">
            <div class="carousel-caption">
                 <div class="btn-group" role="group">
                        <button type="button" class="btn btn-info"><h5>Replace this with your column value</h5></button>
                </div>
            </div>
        </div>
<?php
    $i++; // $i value will be incremental by 1
 } ?>
 </div>