FluidTYPO3\Vhs\ViewHelpers\IfViewHelper::evaluateStack PHP Метод

    protected static function evaluateStack(array $stack)
    {
        $stackCount = count($stack);
        if (0 === $stackCount) {
            return false;
        } elseif (1 === $stackCount) {
            return BooleanNode::convertToBoolean(reset($stack));
        } elseif (3 === $stackCount) {
            list($leftSide, $operator, $rightSide) = array_values($stack);
            if (true === is_string($operator) && true === isset(self::$comparisonOperators[$operator])) {
                $operator = self::$comparisonOperators[$operator];
                return BooleanNode::evaluateComparator($operator, $leftSide, $rightSide);
            }
        }
        $operator = false;
        $operatorPrecedence = PHP_INT_MAX;
        $operatorIndex = false;
        foreach ($stack as $index => $element) {
            if (true === is_string($element) && true === isset(self::$logicalOperators[$element])) {
                $currentOperator = self::$logicalOperators[$element];
                $currentOperatorPrecedence = self::$operatorPrecedence[$currentOperator];
                if ($currentOperatorPrecedence <= $operatorPrecedence) {
                    $operator = $currentOperator;
                    $operatorPrecedence = $currentOperatorPrecedence;
                    $operatorIndex = $index;
                }
            }
        }
        if (false === $operator) {
            throw new \RuntimeException('The stack was not comparable and did not include any logical operators.', 1385071197);
        }
        $operatorIndex = array_search($operatorIndex, array_keys($stack));
        if (0 === $operatorIndex || $operatorIndex + 1 >= $stackCount) {
            throw new \RuntimeException('The stack may not contain a logical operator at the first or last element.', 1385072228);
        }
        $leftSide = array_slice($stack, 0, $operatorIndex);
        $rightSide = array_slice($stack, $operatorIndex + 1);
        return self::evaluateLogicalOperator($leftSide, $operator, $rightSide);
    }