/** * @param StackExpression $set */ private function validateSet(StackExpression $set) { // Set should contain 3 items: "column_name operator value", EG. "level > 200" if ($set->count() !== 3) { throw new InvalidExpressionException($set->asString()); } $arr = $set->get(); if (!$arr[0] instanceof Literal || !$arr[1] instanceof Operator || !$arr[2] instanceof Literal) { throw new InvalidExpressionException($set->asString()); } }