IPv6::compress( string $ip ): string

136    public static function compress($ip)137    {138        // Prepare the IP to be compressed139        $ip = self::uncompress($ip);140        $ip_parts = self::split_v6_v4($ip);141 142        // Replace all leading zeros143        $ip_parts[0] = preg_replace('/(^|:)0+([0-9])/', '\1\2', $ip_parts[0]);144 145        // Find bunches of zeros146        if (preg_match_all('/(?:^|:)(?:0(?::|$))+/', $ip_parts[0], $matches, PREG_OFFSET_CAPTURE)) {147            $max = 0;148            $pos = null;149            foreach ($matches[0] as $match) {150                if (strlen($match[0]) > $max) {151                    $max = strlen($match[0]);152                    $pos = $match[1];153                }154            }155 156            $ip_parts[0] = substr_replace($ip_parts[0], '::', $pos, $max);157        }158 159        if ($ip_parts[1] !== '') {160            return implode(':', $ip_parts);161        }162 163        return $ip_parts[0];164    }