如果语句没有运行代码块？

Question

我试图用$ _GET参数查询表，但是当我添加参数时，没有按指定值排序。如何写这个if语句有什么问题吗？

if (isset($_GET['sort'])) {
    $sorting = $_GET['sort'];
    $result = $mysqli->query("SELECT * FROM routes ORDER BY $sorting");
}
else if (!isset($_GET['sort'])) {
   $result = $mysqli->query("SELECT * FROM routes _");
}    
    if ($result->num_rows != 0) {
        $total_results = $result->num_rows;
        $total_pages   = ceil($total_results / $per_page);


        if (isset($_GET['page']) && is_numeric($_GET['page']) && $_GET['page'] <= $total_pages) {
            $show_page = $_GET['page'];

            if ($show_page > 0 && $show_page <= $total_pages) {
                $start = ($show_page - 1) * $per_page;
                $end   = $start + $per_page;
            } else {
                $start = 0;
                $end   = $per_page;
            }
        } else {

            $start = 0;
            $end   = $per_page;
        }



        echo "<form action='../processors/delete.php' method='post'";
        echo "<br/><table class='table table-striped table-bordered' id='basic-datatable' border='0' cellpadding='10'>";
        echo "<thead><tr> <th>#</th>";
        echo "<th><a href='adminviewer.php?sort=route_id'>Route ID</a></th>";
        echo "<th><a href='adminviewer.php?sort=route_title'>Route</a></th>";
        echo "<th><a href='adminviewer.php?sort=route_price'>Price</a></th>";
        echo "<th><a href='adminviewer.php?sort=route_payment'>Payment</a></th>";
        echo "<th><a href='adminviewer.php?sort=route_net'>Weekly Net</a></th>";
        echo "<th><a href='adminviewer.php?sort=route_city'>City</a></th>";
        echo "<th><a href='adminviewer.php?sort=route_state'>State</a></th>";
        echo "<th><a href='adminviewer.php?sort=route_remarks'>Remarks</a></th>";
        echo "</tr></thead>";

        echo "<tbody>";

        // Check for Sorting Request




        for ($i = $start; $i < $end; $i++) {
            if ($i == $total_results) {
                break;
            }

            $result->data_seek($i);
            $row = $result->fetch_row();


            echo "<tr>";
            echo '<td><input class="checked-box" type="checkbox" name="selec-row[]" value="' . $row[0] . '"></td>';
            echo '<td>' . $row[1] . '</td>';
            echo '<td><a href="detail.php?id=' . $row[0] . '">' . $row[2] . '</a></td>';
            echo '<td>' . $row[3] . '</td>';
            echo '<td>' . $row[4] . '</td>';
            echo '<td>' . $row[5] . '</td>';
            echo '<td>' . $row[6] . '</td>';
            echo '<td>' . $row[7] . '</td>';
            echo '<td>' . $row[8] . '</td>';
            echo "</tr>";


        }

        echo "</tbody>";
        echo "</table>";
        echo "<input class='del-btn' type='submit' value='Delete'>";
        echo "</form>";
    } else {
        echo "No results to display!";
    }


    echo '<div class="col-md-12" style="text-align: center;position:relative;top:-25px;">';
    echo "Showing 1 to " . $per_page . " of " . $total_results . " routes";
    echo '</div>';
    /*  echo '<div class="col-md-6" style="text-align:right;">';
    echo '<ul class="paginated-btns">';
    for ($i = 1; $i <= $total_pages; $i++)
    {
    if (isset($_GET['page']) && $_GET['page'] == $i)
    {
    echo "<li><a href='adminviewer.php?page=$i&page_sel=$per_page'>$i</a></li>";
    }
    else
    {   
    echo "<li><a href='adminviewer.php?page=$i&page_sel=$per_page'>$i</a></li>";
    }

    }
    echo '</ul>';
    */
    echo "</div>";
    echo '</div>';
    echo '</div>';
    echo '</div>';

    echo '<div class="pagination">';

    if (!isset($_GET['page'])) {
        $_GET['page'] = 1;
    }


    if ($_GET['page'] > $per_page) {
        $next_page = $i - 1;
        echo "<div class='pag-btn'><a href='adminviewer.php?page=$next_page&page_sel=$per_page'><- Previous</a></div>";
    } else {
        echo "<div class='pag-btn'>Previous</div>";
    }
    if ($_GET['page'] < $total_pages) {
        $next_page = $_GET['page'] + 1;
        echo "<div class='pag-btn'><a href='adminviewer.php?page=$next_page&page_sel=$per_page'>Next -></a></div>";
    } else {
        echo "<div class='pag-btn'>Next</div>";
    }

    echo '</div>';

我正在学习PHP，所以我可以想象逻辑有问题，但我似乎无法弄明白。

$_GET['sort']的值是表格的列;例如：route_id，route_name，route_price，...