Extract content inside delimiters

extract_unit

    /**
     * Extract content inside delimiters.
     *
     * @param string $start
     * @param string $end
     * @return string Extracted content.
     *
     * @source
     * http://www.bitrepository.com/extract-content-between-two-delimiters-with-php.html
     */
    protected function extract_unit($string, $start, $end)
    {
        $pos        = stripos($string, $start);
        $str        = substr($string, $pos);
        $str_two    = substr($str, strlen($start));
        $second_pos = stripos($str_two, $end);
        $str_three  = substr($str_two, 0, $second_pos);

        return trim($str_three);
    }