/*
(x AND (y OR z)) OR (y AND (x OR z)) OR (z AND (x OR y))
*/
array(
    array(
        'x:=' => $x
        ,array(
            'AND:y:=' => $y
            ,'OR:z:=' => $z
        )
    )
    ,array(
        'OR:y:=' => $y
        ,array(
            'AND:x:=' => $x
            ,'OR:z:=' => $z
        )
    )
    ,array(
        'OR:z:=' => $z
        ,array(
            'AND:x:=' => $x
            ,'OR:y:=' => $y
        )
    )
);