Getting the 'invalid value' error message while submitting email column data with PHP

I’m getting following error on submitting mutation request for “change_multiple_column_values”.
Here is the error details

([data] => Array (
            [change_multiple_column_values] => Array
                ([id] => 1166257859 )
        ) [account_id] => --- )

here is the query and custom value variables

$query = 'mutation ($myBoardID: Int!, $myItemID: Int!, $columnVals: JSON! ) { change_multiple_column_values (item_id: $myItemID board_id:$myBoardID column_values:$columnVals) { id } }';
$vars = [
    'columnVals' => json_encode([
        $monday_com_checkin_status => "Completed",
        $monday_com_checkin_form => [
            'text' => "Phone: " . $_POST['customer_phone'] . "\n" . "Guests List: " . $guests_list . "\n"
        ],
        $monday_com_email_id => [
            'email' => $_POST['customer_email'],
            'text' => $_POST['customer_email']
        ],
    ]),
    'myBoardID' => intval($board_id),
    'myItemID' => intval($item_id),
];

This query is updating all the details correctly but still giving an error in response.

Hi @matteeq!

Could you please share any monday API errors you see?

For more on what these look like, please refer to our Error documentation.