public function advance()
    {
        if ($this->index >= $this->length) {
            throw new LogicException("Argument index out of bounds.");
        }
        return $this->argv[$this->index++];
    }
public function advance()
    {
        if ($this->index >= $this->length) {
            throw new LogicException("Argument index out of bounds.");
        }
        return $this->argv[$this->index++];
    }
Return the current argument and advance to the next position.

@return string