I'm not following you exactly. Is the criteria you're referring to the Search Form Value of the Database Field. I think this is what you're trying to say but I'm not sure.
//keyword array declarations
$KeyArr1 = array("ProductName");
$KeyArr2 = array("ProductSKU");
//comparison list additions
$WADbSearch1->keywordComparison($KeyArr1,"ProductSearch","AND","Includes","%20AND%20","%20OR%20","%22","%22",0);
$WADbSearch1->keywordComparison($KeyArr2,"","OR","Includes",",%20","%20","%22","%22",0);