I'm not quite sure what an html array is, but try the following:
$a = $_POST['htmlarray'];
// unserialize $a
// build sql query up to '...VALUES '
foreach ($a as $row) {
$sql .= '(';
$sql .= implode(',', $row);
$sql .= ')',
}
This should iterate through the arrays and append all your rows to the string. Note, however, that this code does not take care of SQL Injections at all! Not to be meant for production.