public function at($start = null, $length = null)
    {
        return new self(mb_substr((string) $this, $start, $length, 'UTF-8'));
    }
public function at($start = null, $length = null)
    {
        return new self(mb_substr((string) $this, $start, $length, 'UTF-8'));
    }
public function at ( $ start = null , $ length = null ) { return new self ( mb_substr ( ( string ) $ this , $ start , $ length , 'UTF-8' ) ) ; }
Returns part of a string
Known bug in php 5.3.3

@see https://bugs.php.net/bug.php?id=62703

@param int start
@param int $length the length of the string from the starting point

@return KoineString
Returns part of a string Known bug in php 5 . 3 . 3