gzencode - PHP code example

PHP Function Zencode

A function is a piece of code that can be used multiple times and accepts inputs (in the form of arguments) and returns a value. PHP has thousands of built-in functions that can be used to perform various tasks. Functions help in reusability of code, separation of logic and making the code easier to understand.

gzencode() compresses the given string using zlib compressed data format. This is similar to gzip compression but differs in that it doesn't include header information.

The gzip format (which gzencode() follows) has a header containing optional metadata, the DEFLATE compressed data and then a footer with length check and CRC32 checksum. The zlib format (which gzcompress() follows) has a shorter header that only serves to identify the compression format, the DEFLATE compressed data and then the Adler-32 checksum.

The last four bytes of output are the Adler-32 checksum and not the CRC32 as gzip expects. This is because gzencode() uses the zlib library and Mark Adler was one of its authors. Hence it follows the specification whereas gzip uses its own implementation which doesn't.

gzencode example

    // If CSS/JS gzip compression is enabled and the zlib extension is available     // then create a gzipped version of this file. This file is served     // conditionally to browsers that accept gzip using .htaccess rules.     // It's possible that the rewrite rules in .htaccess aren't working on this     // server, but there's no harm (other than the time spent generating the     // file) in generating the file anyway. Sites on servers where rewrite rules     // aren't working can set css.gzip to FALSE in order to skip     // generating a file that won't be used.     if (extension_loaded('zlib') && \Drupal::config('system.performance')->get($file_extension . '.gzip')) {
      try {
        if (!file_exists($uri . '.gz') && !$this->fileSystem->saveData(gzencode($data, 9, FORCE_GZIP), $uri . '.gz', FileSystemInterface::EXISTS_REPLACE)) {
          return FALSE;
        }
      }
      catch (FileException $e) {
        return FALSE;
      }
    }
    return $uri;
  }

}

'data' => $profile->getCollectors(),
            'ip' => $profile->getIp(),
            'method' => $profile->getMethod(),
            'url' => $profile->getUrl(),
            'time' => $profile->getTime(),
            'status_code' => $profile->getStatusCode(),
        ];

        $data = serialize($data);

        if (\function_exists('gzencode')) {
            $data = gzencode($data, 3);
        }

        if (false === file_put_contents($file, $data, \LOCK_EX)) {
            return false;
        }

        if (!$profileIndexed) {
            // Add to index             if (false === $file = fopen($this->getIndexFilename(), 'a')) {
                return false;
            }

wp_die();
        } elseif ( 2 == $_GET['test'] ) {
            if ( ! isset( $_SERVER['HTTP_ACCEPT_ENCODING'] ) ) {
                wp_die( -1 );
            }

            if ( false !== stripos( $_SERVER['HTTP_ACCEPT_ENCODING'], 'deflate' ) && function_exists( 'gzdeflate' ) && ! $force_gzip ) {
                header( 'Content-Encoding: deflate' );
                $out = gzdeflate( $test_str, 1 );
            } elseif ( false !== stripos( $_SERVER['HTTP_ACCEPT_ENCODING'], 'gzip' ) && function_exists( 'gzencode' ) ) {
                header( 'Content-Encoding: gzip' );
                $out = gzencode( $test_str, 1 );
            } else {
                wp_die( -1 );
            }

            echo $out;
            wp_die();
        } elseif ( 'no' === $_GET['test'] ) {
            check_ajax_referer( 'update_can_compress_scripts' );
            // Use `update_option()` on single site to mark the option for autoloading.             if ( is_multisite() ) {
                update_site_option( 'can_compress_scripts', 0 );
            }

throw new DatabaseException('The file compression format you chose is not supported by your server.');
            }

            $prefs['format'] = 'txt';
        }

        if ($prefs['format'] === 'txt') {
            return $this->_backup($prefs);
        }

        // @TODO gzencode() requires `ext-zlib`, but _backup() is not implemented in all databases.         return gzencode($this->_backup($prefs));
    }

    /** * Platform dependent version of the backup function. * * @return mixed */
    abstract public function _backup(?array $prefs = null);
}