HeaderCallback.php

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<?php
 
namespace MediaWiki;
 
class HeaderCallback {
    private static $headersSentException;
    private static $messageSent = false;
 
    public static function register() {
        header_register_callback( [ __CLASS__, 'callback' ] );
    }
 
    public static function callback() {
        // Prevent caching of responses with cookies (T127993)
        $headers = [];
        foreach ( headers_list() as $header ) {
            list( $name, $value ) = explode( ':', $header, 2 );
            $headers[strtolower( trim( $name ) )][] = trim( $value );
        }
 
        if ( isset( $headers['set-cookie'] ) ) {
            $cacheControl = isset( $headers['cache-control'] )
                ? implode( ', ', $headers['cache-control'] )
                : '';
 
            if ( !preg_match( '/(?:^|,)\s*(?:private|no-cache|no-store)\s*(?:$|,)/i',
                $cacheControl )
            ) {
                header( 'Expires: Thu, 01 Jan 1970 00:00:00 GMT' );
                header( 'Cache-Control: private, max-age=0, s-maxage=0' );
                \MediaWiki\Logger\LoggerFactory::getInstance( 'cache-cookies' )->warning(
                    'Cookies set on {url} with Cache-Control "{cache-control}"', [
                        'url' => \WebRequest::getGlobalRequestURL(),
                        'cookies' => $headers['set-cookie'],
                        'cache-control' => $cacheControl ?: '<not set>',
                    ]
                );
            }
        }
 
        // Save a backtrace for logging in case it turns out that headers were sent prematurely
        self::$headersSentException = new \Exception( 'Headers already sent from this point' );
    }
 
    public static function warnIfHeadersSent() {
        if ( headers_sent() && !self::$messageSent ) {
            self::$messageSent = true;
            \MWDebug::warning( 'Headers already sent, should send headers earlier than ' .
                wfGetCaller( 3 ) );
            $logger = \MediaWiki\Logger\LoggerFactory::getInstance( 'headers-sent' );
            $logger->error( 'Warning: headers were already sent from the location below', [
                'exception' => self::$headersSentException,
                'detection-trace' => new \Exception( 'Detected here' ),
            ] );
        }
    }
}