将PHP字符串传递给具有多个值的SQL？

I have a situation in some really old code of mine where I am trying to pass through the data from a string and do a DB query off of those values.

The data loads correctly if I set $hula = '7630' but when I set it to multiple values in a string like $hula = '7890, 5630' I get error (Message: db2_execute(): Statement Execute Failed)

I clearly know I am missing something here but I am CLEARLY not seeing it. Thanks

<?php
    $hula = '7890, 5630';
    $stmt = "SELECT TXLCT2, ZFDLDS FROM ".$ArEnviro>getDataLibFin().".TXPL6C2, ".
    $ArEnviro->getDataLibFin().".HXPTABLD WHERE TXLCT2 = CFDECD AND CFDTCD = 'YCT2' AND TXLLV6 IN ? ORDER BY TXLCT2";
    $preparedStmt = db_prepare($ArConnections->getDB2ConnResource(),$stmt);
    $result = db_execute($preparedStmt, [$hula]);
    while(($row = db_fetch_both($preparedStmt)) == true) {
    echo('<option value="'.htmlspecialchars($row["TXLCT2"]).'">'.htmlspecialchars($row["TXLCT2"]).' - '.htmlspecialchars($row["ZFDLDS"]).'</option>');
}
?>

A simple change:

if TXLLV6 is integer:

$hula = '(7890, 5630)';

If it is varchar or any kind of string:

$hula = "('7890', '5630')";