为什么undefined没有被删除

I see this error:

Notice: Undefined index: pageno in C:\xampp\htdocs\ims\public\includes\process.php on line 81 You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near '-5,5' at line 1

    //manage category
if(isset($_POST["manageCategory"])){

    $m = new Manage();
    $result = $m->manageRecordWithPagination("categories",$_POST["pageno"]);
    $rows = $result["rows"];
    $pagination = $result["pagination"];

    if(count($rows)> 0){
        $n = 0;
        foreach ($rows as $row){
    ?>
      <tr>
        <td><?php echo ++$n; ?></td>
        <td><?php echo $row["category"]; ?></td>
        <td><?php echo $row["parent"]; ?></td>
        <td><a href="#" class="btn btn-success btn-sm">Active</a></td>
        <td>
         <a href ="#" did="" class="btn btn-danger btn-sm">Delete</a>
         <a href ="#" class="btn btn-info btn-sm">Edit</a>
        </td>
      </tr>

    <?php

        }
        ?>

        <tr><td colspan="5"><?php echo $pagination; ?></td></tr>
        <?php
        exit();
    }

There are high possibility that "pageno" is not defined in your $_POST , so to check this you need to run this statement :

print_r($_POST);

Kindly check its existence.