Title: WP_Http_Encoding
Published: April 25, 2014
Last modified: April 28, 2025

---

# class WP_Http_Encoding {}

## In this article

 * [Description](https://developer.wordpress.org/reference/classes/wp_http_encoding/?output_format=md#description)
 * [Methods](https://developer.wordpress.org/reference/classes/wp_http_encoding/?output_format=md#methods)
 * [Source](https://developer.wordpress.org/reference/classes/wp_http_encoding/?output_format=md#source)
 * [Changelog](https://developer.wordpress.org/reference/classes/wp_http_encoding/?output_format=md#changelog)

[ Back to top](https://developer.wordpress.org/reference/classes/wp_http_encoding/?output_format=md#wp--skip-link--target)

Core class used to implement deflate and gzip transfer encoding support for HTTP
requests.

## 󠀁[Description](https://developer.wordpress.org/reference/classes/wp_http_encoding/?output_format=md#description)󠁿

Includes RFC 1950, RFC 1951, and RFC 1952.

## 󠀁[Methods](https://developer.wordpress.org/reference/classes/wp_http_encoding/?output_format=md#methods)󠁿

| Name | Description | 
| [WP_Http_Encoding::accept_encoding](https://developer.wordpress.org/reference/classes/wp_http_encoding/accept_encoding/) | What encoding types to accept and their priority values. | 
| [WP_Http_Encoding::compatible_gzinflate](https://developer.wordpress.org/reference/classes/wp_http_encoding/compatible_gzinflate/) | Decompression of deflated string while staying compatible with the majority of servers. | 
| [WP_Http_Encoding::compress](https://developer.wordpress.org/reference/classes/wp_http_encoding/compress/) | Compress raw string using the deflate format. | 
| [WP_Http_Encoding::content_encoding](https://developer.wordpress.org/reference/classes/wp_http_encoding/content_encoding/) | What encoding the content used when it was compressed to send in the headers. | 
| [WP_Http_Encoding::decompress](https://developer.wordpress.org/reference/classes/wp_http_encoding/decompress/) | Decompression of deflated string. | 
| [WP_Http_Encoding::is_available](https://developer.wordpress.org/reference/classes/wp_http_encoding/is_available/) | Whether decompression and compression are supported by the PHP version. | 
| [WP_Http_Encoding::should_decode](https://developer.wordpress.org/reference/classes/wp_http_encoding/should_decode/) | Whether the content be decoded based on the headers. |

## 󠀁[Source](https://developer.wordpress.org/reference/classes/wp_http_encoding/?output_format=md#source)󠁿

    ```php
    class WP_Http_Encoding {

    	/**
    	 * Compress raw string using the deflate format.
    	 *
    	 * Supports the RFC 1951 standard.
    	 *
    	 * @since 2.8.0
    	 *
    	 * @param string $raw      String to compress.
    	 * @param int    $level    Optional. Compression level, 9 is highest. Default 9.
    	 * @param string $supports Optional, not used. When implemented it will choose
    	 *                         the right compression based on what the server supports.
    	 * @return string|false Compressed string on success, false on failure.
    	 */
    	public static function compress( $raw, $level = 9, $supports = null ) {
    		return gzdeflate( $raw, $level );
    	}

    	/**
    	 * Decompression of deflated string.
    	 *
    	 * Will attempt to decompress using the RFC 1950 standard, and if that fails
    	 * then the RFC 1951 standard deflate will be attempted. Finally, the RFC
    	 * 1952 standard gzip decode will be attempted. If all fail, then the
    	 * original compressed string will be returned.
    	 *
    	 * @since 2.8.0
    	 *
    	 * @param string $compressed String to decompress.
    	 * @param int    $length     The optional length of the compressed data.
    	 * @return string|false Decompressed string on success, false on failure.
    	 */
    	public static function decompress( $compressed, $length = null ) {

    		if ( empty( $compressed ) ) {
    			return $compressed;
    		}

    		$decompressed = @gzinflate( $compressed );
    		if ( false !== $decompressed ) {
    			return $decompressed;
    		}

    		$decompressed = self::compatible_gzinflate( $compressed );
    		if ( false !== $decompressed ) {
    			return $decompressed;
    		}

    		$decompressed = @gzuncompress( $compressed );
    		if ( false !== $decompressed ) {
    			return $decompressed;
    		}

    		if ( function_exists( 'gzdecode' ) ) {
    			$decompressed = @gzdecode( $compressed );

    			if ( false !== $decompressed ) {
    				return $decompressed;
    			}
    		}

    		return $compressed;
    	}

    	/**
    	 * Decompression of deflated string while staying compatible with the majority of servers.
    	 *
    	 * Certain Servers will return deflated data with headers which PHP's gzinflate()
    	 * function cannot handle out of the box. The following function has been created from
    	 * various snippets on the gzinflate() PHP documentation.
    	 *
    	 * Warning: Magic numbers within. Due to the potential different formats that the compressed
    	 * data may be returned in, some "magic offsets" are needed to ensure proper decompression
    	 * takes place. For a simple pragmatic way to determine the magic offset in use, see:
    	 * https://core.trac.wordpress.org/ticket/18273
    	 *
    	 * @since 2.8.1
    	 *
    	 * @link https://core.trac.wordpress.org/ticket/18273
    	 * @link https://www.php.net/manual/en/function.gzinflate.php#70875
    	 * @link https://www.php.net/manual/en/function.gzinflate.php#77336
    	 *
    	 * @param string $gz_data String to decompress.
    	 * @return string|false Decompressed string on success, false on failure.
    	 */
    	public static function compatible_gzinflate( $gz_data ) {

    		// Compressed data might contain a full header, if so strip it for gzinflate().
    		if ( str_starts_with( $gz_data, "\x1f\x8b\x08" ) ) {
    			$i   = 10;
    			$flg = ord( substr( $gz_data, 3, 1 ) );
    			if ( $flg > 0 ) {
    				if ( $flg & 4 ) {
    					list($xlen) = unpack( 'v', substr( $gz_data, $i, 2 ) );
    					$i          = $i + 2 + $xlen;
    				}
    				if ( $flg & 8 ) {
    					$i = strpos( $gz_data, "\0", $i ) + 1;
    				}
    				if ( $flg & 16 ) {
    					$i = strpos( $gz_data, "\0", $i ) + 1;
    				}
    				if ( $flg & 2 ) {
    					$i = $i + 2;
    				}
    			}
    			$decompressed = @gzinflate( substr( $gz_data, $i, -8 ) );
    			if ( false !== $decompressed ) {
    				return $decompressed;
    			}
    		}

    		// Compressed data from java.util.zip.Deflater amongst others.
    		$decompressed = @gzinflate( substr( $gz_data, 2 ) );
    		if ( false !== $decompressed ) {
    			return $decompressed;
    		}

    		return false;
    	}

    	/**
    	 * What encoding types to accept and their priority values.
    	 *
    	 * @since 2.8.0
    	 *
    	 * @param string $url
    	 * @param array  $args
    	 * @return string Types of encoding to accept.
    	 */
    	public static function accept_encoding( $url, $args ) {
    		$type                = array();
    		$compression_enabled = self::is_available();

    		if ( ! $args['decompress'] ) { // Decompression specifically disabled.
    			$compression_enabled = false;
    		} elseif ( $args['stream'] ) { // Disable when streaming to file.
    			$compression_enabled = false;
    		} elseif ( isset( $args['limit_response_size'] ) ) { // If only partial content is being requested, we won't be able to decompress it.
    			$compression_enabled = false;
    		}

    		if ( $compression_enabled ) {
    			if ( function_exists( 'gzinflate' ) ) {
    				$type[] = 'deflate;q=1.0';
    			}

    			if ( function_exists( 'gzuncompress' ) ) {
    				$type[] = 'compress;q=0.5';
    			}

    			if ( function_exists( 'gzdecode' ) ) {
    				$type[] = 'gzip;q=0.5';
    			}
    		}

    		/**
    		 * Filters the allowed encoding types.
    		 *
    		 * @since 3.6.0
    		 *
    		 * @param string[] $type Array of what encoding types to accept and their priority values.
    		 * @param string   $url  URL of the HTTP request.
    		 * @param array    $args HTTP request arguments.
    		 */
    		$type = apply_filters( 'wp_http_accept_encoding', $type, $url, $args );

    		return implode( ', ', $type );
    	}

    	/**
    	 * What encoding the content used when it was compressed to send in the headers.
    	 *
    	 * @since 2.8.0
    	 *
    	 * @return string Content-Encoding string to send in the header.
    	 */
    	public static function content_encoding() {
    		return 'deflate';
    	}

    	/**
    	 * Whether the content be decoded based on the headers.
    	 *
    	 * @since 2.8.0
    	 *
    	 * @param array|string $headers All of the available headers.
    	 * @return bool
    	 */
    	public static function should_decode( $headers ) {
    		if ( is_array( $headers ) ) {
    			if ( array_key_exists( 'content-encoding', $headers ) && ! empty( $headers['content-encoding'] ) ) {
    				return true;
    			}
    		} elseif ( is_string( $headers ) ) {
    			return ( stripos( $headers, 'content-encoding:' ) !== false );
    		}

    		return false;
    	}

    	/**
    	 * Whether decompression and compression are supported by the PHP version.
    	 *
    	 * Each function is tested instead of checking for the zlib extension, to
    	 * ensure that the functions all exist in the PHP version and aren't
    	 * disabled.
    	 *
    	 * @since 2.8.0
    	 *
    	 * @return bool
    	 */
    	public static function is_available() {
    		return ( function_exists( 'gzuncompress' ) || function_exists( 'gzdeflate' ) || function_exists( 'gzinflate' ) );
    	}
    }
    ```

[View all references](https://developer.wordpress.org/reference/files/wp-includes/class-wp-http-encoding.php/)
[View on Trac](https://core.trac.wordpress.org/browser/tags/6.9.4/src/wp-includes/class-wp-http-encoding.php#L18)
[View on GitHub](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/class-wp-http-encoding.php#L18-L234)

## 󠀁[Changelog](https://developer.wordpress.org/reference/classes/wp_http_encoding/?output_format=md#changelog)󠁿

| Version | Description | 
| [2.8.0](https://developer.wordpress.org/reference/since/2.8.0/) | Introduced. |

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