src/Helpers/Request/ArrayHelper.php
public function isIn($needle, $haystack, $strict = false)
    {
        return $this->proxy(__FUNCTION__, [$needle, $haystack, $strict]);
    }
public function isIn($needle, $haystack, $strict = false)
    {
        return $this->proxy(__FUNCTION__, [$needle, $haystack, $strict]);
    }
Check whether an array or [[\Traversable]] contains an element.

This method does the same as the PHP function [in_array()](http://php.net/manual/en/function.in-array.php)
but additionally works for objects that implement the [[\Traversable]] interface.
@param mixed $needle The value to look for.
@param array|\Traversable $haystack The set of values to search.
@param bool $strict Whether to enable strict (`===`) comparison.
@return bool `true` if `$needle` was found in `$haystack`, `false` otherwise.
@throws InvalidArgumentException if `$haystack` is neither traversable nor an array.
@see http://php.net/manual/en/function.in-array.php
@see \Reaction\Helpers\ArrayHelper::isIn()