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<?php
/**
* Functions to be used with PHP's output buffer.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
* http://www.gnu.org/copyleft/gpl.html
*
* @file
*/
namespace MediaWiki\Output;
use MediaWiki\Logger\LoggerFactory;
use MediaWiki\MainConfigNames;
use MediaWiki\MediaWikiServices;
/**
* @since 1.31
*/
class OutputHandler {
/**
* Standard output handler for use with ob_start.
*
* Output buffers using this method should only be started from MW_SETUP_CALLBACK,
* and only if there are no parent output buffers.
*
* @param string $s Web response output
* @param int $phase Flags indicating the reason for the call
* @return string
*/
public static function handle( $s, $phase ) {
$config = MediaWikiServices::getInstance()->getMainConfig();
$disableOutputCompression = $config->get( MainConfigNames::DisableOutputCompression );
// Don't send headers if output is being discarded (T278579)
if ( ( $phase & PHP_OUTPUT_HANDLER_CLEAN ) === PHP_OUTPUT_HANDLER_CLEAN ) {
$logger = LoggerFactory::getInstance( 'output' );
$logger->debug( __METHOD__ . " entrypoint={entry}; size={size}; phase=$phase", [
'entry' => MW_ENTRY_POINT,
'size' => strlen( $s ),
] );
return $s;
}
// Check if a compression output buffer is already enabled via php.ini. Such
// buffers exists at the start of the request and are reflected by ob_get_level().
$phpHandlesCompression = (
ini_get( 'output_handler' ) === 'ob_gzhandler' ||
ini_get( 'zlib.output_handler' ) === 'ob_gzhandler' ||
!in_array(
strtolower( ini_get( 'zlib.output_compression' ) ),
[ '', 'off', '0' ]
)
);
if (
// Compression is not already handled by an internal PHP buffer
!$phpHandlesCompression &&
// Compression is not disabled by the application entry point
!defined( 'MW_NO_OUTPUT_COMPRESSION' ) &&
// Compression is not disabled by site configuration
!$disableOutputCompression
) {
$s = self::handleGzip( $s );
}
if (
// Response body length does not depend on internal PHP compression buffer
!$phpHandlesCompression &&
// Response body length does not depend on mangling by a custom buffer
!ini_get( 'output_handler' ) &&
!ini_get( 'zlib.output_handler' )
) {
self::emitContentLength( strlen( $s ) );
}
return $s;
}
/**
* Get the "file extension" that some client apps will estimate from
* the currently-requested URL.
*
* This isn't a WebRequest method, because we need it before the class loads.
* @todo As of 2018, this actually runs after autoloader in Setup.php, so
* WebRequest seems like a good place for this.
*
* @return string
*/
private static function findUriExtension() {
// @todo FIXME: this sort of dupes some code in WebRequest::getRequestUrl()
if ( isset( $_SERVER['REQUEST_URI'] ) ) {
// Strip the query string...
$path = explode( '?', $_SERVER['REQUEST_URI'], 2 )[0];
} elseif ( isset( $_SERVER['SCRIPT_NAME'] ) ) {
// Probably IIS. QUERY_STRING appears separately.
$path = $_SERVER['SCRIPT_NAME'];
} else {
// Can't get the path from the server? :(
return '';
}
$period = strrpos( $path, '.' );
if ( $period !== false ) {
return strtolower( substr( $path, $period ) );
}
return '';
}
/**
* Handler that compresses data with gzip if allowed by the Accept header.
*
* Unlike ob_gzhandler, it works for HEAD requests too. This assumes that the application
* processes them as normal GET request and that the webserver is tasked with stripping out
* the response body before sending the response the client.
*
* @param string $s Web response output
* @return string
*/
private static function handleGzip( $s ) {
if ( !function_exists( 'gzencode' ) ) {
wfDebug( __METHOD__ . "() skipping compression (gzencode unavailable)" );
return $s;
}
if ( headers_sent() ) {
wfDebug( __METHOD__ . "() skipping compression (headers already sent)" );
return $s;
}
$ext = self::findUriExtension();
if ( $ext == '.gz' || $ext == '.tgz' ) {
// Don't do gzip compression if the URL path ends in .gz or .tgz
// This confuses Safari and triggers a download of the page,
// even though it's pretty clearly labeled as viewable HTML.
// Bad Safari! Bad!
return $s;
}
if ( $s === '' ) {
// Do not gzip empty HTTP responses since that would not only bloat the body
// length, but it would result in invalid HTTP responses when the HTTP status code
// is one that must not be accompanied by a body (e.g. "204 No Content").
return $s;
}
if ( wfClientAcceptsGzip() ) {
wfDebug( __METHOD__ . "() is compressing output" );
header( 'Content-Encoding: gzip' );
$s = gzencode( $s, 6 );
}
// Set vary header if it hasn't been set already
$headers = headers_list();
$foundVary = false;
foreach ( $headers as $header ) {
$headerName = strtolower( substr( $header, 0, 5 ) );
if ( $headerName == 'vary:' ) {
$foundVary = true;
break;
}
}
if ( !$foundVary ) {
header( 'Vary: Accept-Encoding' );
}
return $s;
}
/**
* Set the Content-Length header if possible
*
* This sets Content-Length for the following cases:
* - When the response body is meaningful (HTTP 200/404).
* - On any HTTP 1.0 request response. This improves cooperation with certain CDNs.
*
* This assumes that HEAD requests are processed as GET requests by MediaWiki and that
* the webserver is tasked with stripping out the body.
*
* Setting Content-Length can prevent clients from getting stuck waiting on PHP to finish
* while deferred updates are running.
*
* @param int $length
*/
private static function emitContentLength( $length ) {
if ( headers_sent() ) {
wfDebug( __METHOD__ . "() headers already sent" );
return;
}
if (
in_array( http_response_code(), [ 200, 404 ], true ) ||
( $_SERVER['SERVER_PROTOCOL'] ?? null ) === 'HTTP/1.0'
) {
header( "Content-Length: $length" );
}
}
}
/** @deprecated class alias since 1.41 */
class_alias( OutputHandler::class, 'MediaWiki\\OutputHandler' );
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