Notice: Undefined index: check7456 in php [duplicate]

I am getting a notice at Line A in the php code below. "Notice: Undefined index: check7456 at Line A".

At Line B, we are checking $list is an array or not.

foreach ($_POST['rows'] as $AB_CD) {
    $data = $dbo->execStmt("SELECT AB_NO, INFO, CAPACITY FROM TABLE_NAME1 WHERE AB_CD = {$AB_CD}");

    $document = new Document($db, 'EDR', $data['AB_NO'][0], $data['INFO'][0], $data['CAPACITY'][0]);

    $list = $_POST["check{$AB_CD}"];   // Line A

    foreach ($values as $name) {
        if (is_array($list) && in_array($name, $list)) {    // Line B
            $document->helloWorld('Good Day', $name);
        } else {
            $document->removeHelloWorld('Good Day', $name);
        }
    }
}

Problem Statement:

I am wondering what changes I need to do at Line A so that I can avoid this notice.

source https://stackoverflow.com/questions/75816162/notice-undefined-index-check7456-in-php