code: public function execute(array $arguments) {
  		if (empty($arguments)) throw new \BadFunctionCallException("IsA: No parameters found.");
  		if (!array_key_exists(1, $arguments)) throw new \BadFunctionCallException("IsA: No classname has been specified.");
  		if (!is_string($arguments[1]))
  			throw new \InvalidArgumentException(sprintf("IsA: Expected a value of type string as second argument, %s found instead.", gettype($arguments[1])));
  		if (!is_object($arguments[0])) return false;
  		return is_a($arguments[0], $arguments[1]);
  	}
docs: Determines if a given value is an instance of a specified class
  Usage: (is-a "ArrayObject" _value)
  Returns: boolean
  (non-PHPdoc)
  @see \eMacros\Runtime\GenericFunction::execute()