src/Helpers/Request/StringHelper.php
public function byteSubstr($string, $start, $length = null)
    {
        return $this->proxy(__FUNCTION__, [$string, $start, $length]);
    }
public function byteSubstr($string, $start, $length = null)
    {
        return $this->proxy(__FUNCTION__, [$string, $start, $length]);
    }
Returns the portion of string specified by the start and length parameters.
This method ensures the string is treated as a byte array by using `mb_substr()`.
@param string $string the input string. Must be one character or longer.
@param int $start the starting position
@param int $length the desired portion length. If not specified or `null`, there will be
no limit on length i.e. the output will be until the end of the string.
@return string the extracted part of string, or FALSE on failure or an empty string.
@see http://www.php.net/manual/en/function.substr.php
@see \Reaction\Helpers\StringHelper::byteSubstr()