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GZIP-Kompression für statische Dateien mit mod_rewrite und PHP

Florian Höch — Sun, 03 Jun 2012 17:05:10 +0000

Dieses PHP-Skript hat sich seit seiner Erstveröffentlichung geändert. Zur neuesten Version des GZIP-Komprimierungs-Skripts auf github.

View english version of this article

Um Bandbreite zu sparen und die Downloadgeschwindigkeit zu erhöhen, lohnt es sich, auch statische Dateien wie Stylesheets und JavaScripts mit GZIP zu komprimieren und eine sinnvolle Cache-Verweildauer festzulegen. Das lässt sich mit einer angepassten .htacces-Datei gut automatisieren. Hierbei kann man entweder auf die dynamische Kompression mittels Apache mod_deflate oder aber eine Alternativlösung (in diesem Fall ein PHP-Skript) zurückgreifen. Ich habe mich für die PHP-Lösung entschieden, da ich die komprimierten Daten so im Dateisystem ablegen kann und etwas Prozessorleistung für die dynamische Kompression spare, die sonst mit mod_deflate bei jedem Dateizugriff erfolgt (und nicht nur beim ersten oder bei Änderungen, was den Vorteil der PHP-Lösung ausmacht).

Das PHP-Skript, das sich um die Kompression der angefragten Dateien kümmert und sie als statische .gz-Dateien auf dem Server ablegt, sieht wie folgt aus:

PHP-Skript

 'text/css; charset=UTF-8',
                           'html' => 'text/html; charset=UTF-8',
                           'gif' => 'image/gif',
                           'ico' => 'image/x-icon',
                           'jpg' => 'image/jpeg',
                           'jpeg' => 'image/jpeg',
                           'js' => 'application/javascript',
                           'json' => 'application/json',
                           'png' => 'image/png',
                           'txt' => 'text/plain',
                           'xml' => 'application/xml');
    if (empty($content_types[$info['extension']]))
        return 'text/html; charset=UTF-8';
    return $content_types[$info['extension']];
}

function main() {
    // Get file path by stripping query parameters from the request URI
    if (!empty($_SERVER['REQUEST_URI']))
        $path = preg_replace('/\/?(?:\?.*)?$/', '', $_SERVER['REQUEST_URI']);

    // If the path is empty, either use DEFAULT_FILENAME if defined, or exit
    if (empty($path)) {
        if (defined('DEFAULT_FILENAME')) $path = '/' . DEFAULT_FILENAME;
        else die();
    }

    $file = dirname(__FILE__) . $path;
    if (!file_exists($file)) die();

    $mtime = filemtime($file);

    // If the user agent sent a IF_MODIFIED_SINCE header, check if the file
    // has been modified. If it hasn't, send '304 Not Modified' header & exit
    if (!empty($_SERVER['HTTP_IF_MODIFIED_SINCE']) &&
        $mtime <= strtotime($_SERVER['HTTP_IF_MODIFIED_SINCE'])) {
        header($_SERVER['SERVER_PROTOCOL'] . ' 304 Not Modified', true, 304);
        exit;
    }
    
    // Determine Content-Type based on file extension
    $content_type = get_content_type($file);

    // If the user agent accepts GZIP encoding, store a compressed version of
    // the file (.gz)
    if (!empty($_SERVER['HTTP_ACCEPT_ENCODING']) &&
        in_array('gzip', preg_split('/\s*,\s*/',
                                    $_SERVER['HTTP_ACCEPT_ENCODING']))) {
        // Only write the compressed version if it does not yet exist or the
        // original file has changed
        $gzfile = $file . '.gz';
        if (!file_exists($gzfile) || filemtime($gzfile) < $mtime)
            file_put_contents($gzfile, gzencode(file_get_contents($file)));
        // Send compression headers and use the .gz file instead of the
        // original filename
        header('Content-Encoding: gzip');
        $file = $file . '.gz';
    }

    // Vary max-age and expiration headers based on content type
    switch ($content_type) {
        case 'image/gif':
        case 'image/jpeg':
        case 'image/png':
            // Max-age for images: 31 days
            $maxage = 60 * 60 * 24 * 31;
            break;
        default:
            // Max-age for everything else: 7 days
            $maxage = 60 * 60 * 24 * 7;
    }

    // Send remaining headers
    header('Vary: Accept-Encoding');
    header('Cache-Control: max-age=' . $maxage);
    header('Expires: ' . gmdate('D, d M Y H:i:s', time() + $maxage) . ' GMT');
    header('Last-Modified: ' . gmdate('D, d M Y H:i:s', $mtime) . ' GMT');
    header('Content-Type: ' . $content_type);
    header('Content-Length: ' . filesize($file));
    
    // If the request method isn't HEAD, send the file contents
    if ($_SERVER['REQUEST_METHOD'] != 'HEAD') readfile($file);
}

main();

?>

Das Skript sollte als ‚gz.php‘ im Wurzelverzeichnis der WordPress-Installation liegen. Es erkennt, wann eine Datei geändert wurde und komprimiert diese nur dann erneut. Ausserdem sendet es eine ‚304 Not Modified‘-Antwort, falls eine angefragte Datei seit der letzten Anfrage nicht verändert wurde.

Dann benötigen wir eine angepasste .htaccess-Datei. Für meine WordPress-Installation sieht diese wie folgt aus:

.htaccess-Datei

# Set 'Vary' response header for .gz files


Header always append Vary "Accept-Encoding"




ExpiresActive On
ExpiresByType application/json "access plus 1 week"
ExpiresByType application/x-javascript "access plus 1 week"
ExpiresByType application/xml "access plus 1 week"
ExpiresByType image/gif "access plus 1 month"
ExpiresByType image/jpeg "access plus 1 month"
ExpiresByType image/png "access plus 1 month"
ExpiresByType image/x-icon "access plus 1 month"
ExpiresByType text/css "access plus 1 week"
ExpiresByType text/html "access plus 1 week"
ExpiresByType text/plain "access plus 1 week"


# BEGIN WordPress

RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]

# END WordPress

# BEGIN GZIP

# If the user agent accepts gzip encoding...
RewriteCond %{HTTP:Accept-Encoding} gzip
# ...and the requested file exists...
RewriteCond %{REQUEST_FILENAME} -f
# ...then use a PHP script serve a compressed version. Done.
RewriteRule \.(css|html|ico|js|json|txt|xml)$ /gz.php [L]

# END GZIP

Für .gz-Dateizugriffe wird der ‚Vary‘-Header festgelegt, um korrektes Caching über Proxy-Server zu gewährleisten. Dann folgen einige Direktiven zur Cache-Verweildauer (‚Expires‘- bzw. ‚Cache-Control‘-Header), diese lassen sich nach eigenem Gusto anpassen. Im Beispiel laufen CSS- und JS-Dateien nach einer Woche im Cache ab, Bilddateien nach einem Monat.

Alternativ lässt sich die mod_rewrite-Direktive für das PHP-Skript auch so ändern, dass nur der erste Zugriff einen Aufruf des Skripts erzeugt, und danach direkt die erstellte .gz-Datei abgerufen wird. Dazu die Zeilen zwischen # BEGIN GZIP und # END GZIP in dem .htaccess-Beispiel oben durch folgende Zeilen ersetzen:


# If the user agent accepts gzip encoding...
RewriteCond %{HTTP:Accept-Encoding} gzip
# ...and if gzip-encoded version of the requested file exists (.gz)...
RewriteCond %{REQUEST_FILENAME}.gz -f
# ...then serve the gzip-encoded file. Done.
RewriteRule ^(.+)$ $1.gz [L]
# Or if the user agent accepts gzip encoding...
RewriteCond %{HTTP:Accept-Encoding} gzip
# ...and the requested file exists...
RewriteCond %{REQUEST_FILENAME} -f
# ...then use a PHP script serve a compressed version. Done.
RewriteRule \.(css|html|ico|js|json|txt|xml)$ /gz.php [L]

Bildnachweis: .gz-Icon basierend auf generischem Paket-Icon aus GNOME 2.18 Icon Theme, veröffentlicht unter GNU GPL 2.0 Lizenz

Dieser Beitrag wurde unter Creative Commons Namensnennung-Nicht-kommerziell-Weitergabe unter gleichen Bedingungen 3.0 Deutschland Lizenz veröffentlicht.

Der Beitrag GZIP-Kompression für statische Dateien mit mod_rewrite und PHP erschien zuerst bei hoech.net.

GZIP compression of static assets via mod_rewrite and PHP

Florian Höch — Sun, 03 Jun 2012 17:05:16 +0000

This PHP script has changed since its initial release. You can find the latest version of the GZIP compression script on github.

Zur deutschen Version dieses Artikels

To conserve bandwidth and speed up page loading, it pays off to also compress static files like stylesheets and scripts in addition to the page itself with GZIP and set meaningful cache retention times. With Apache, this process can be set up with a custom .htaccess file as dynamic on-the-fly compression with either mod_deflate, or alernatively via PHP. In my case I settled with a PHP solution which stores the compressed data on disk, so repeated requests don’t cause the files to be compressed over and over again, but only on first access (or if the file has changed).

The PHP script which takes care of the compression of requested files and stores the compressed data as .gz files on disk looks like this:

PHP script

 'text/css; charset=UTF-8',
                           'html' => 'text/html; charset=UTF-8',
                           'gif' => 'image/gif',
                           'ico' => 'image/x-icon',
                           'jpg' => 'image/jpeg',
                           'jpeg' => 'image/jpeg',
                           'js' => 'application/javascript',
                           'json' => 'application/json',
                           'png' => 'image/png',
                           'txt' => 'text/plain',
                           'xml' => 'application/xml');
    if (empty($content_types[$info['extension']]))
        return 'text/html; charset=UTF-8';
    return $content_types[$info['extension']];
}

function main() {
    // Get file path by stripping query parameters from the request URI
    if (!empty($_SERVER['REQUEST_URI']))
        $path = preg_replace('/\/?(?:\?.*)?$/', '', $_SERVER['REQUEST_URI']);

    // If the path is empty, either use DEFAULT_FILENAME if defined, or exit
    if (empty($path)) {
        if (defined('DEFAULT_FILENAME')) $path = '/' . DEFAULT_FILENAME;
        else die();
    }

    $file = dirname(__FILE__) . $path;
    if (!file_exists($file)) die();

    $mtime = filemtime($file);

    // If the user agent sent a IF_MODIFIED_SINCE header, check if the file
    // has been modified. If it hasn't, send '304 Not Modified' header & exit
    if (!empty($_SERVER['HTTP_IF_MODIFIED_SINCE']) &&
        $mtime <= strtotime($_SERVER['HTTP_IF_MODIFIED_SINCE'])) {
        header($_SERVER['SERVER_PROTOCOL'] . ' 304 Not Modified', true, 304);
        exit;
    }
    
    // Determine Content-Type based on file extension
    $content_type = get_content_type($file);

    // If the user agent accepts GZIP encoding, store a compressed version of
    // the file (.gz)
    if (!empty($_SERVER['HTTP_ACCEPT_ENCODING']) &&
        in_array('gzip', preg_split('/\s*,\s*/',
                                    $_SERVER['HTTP_ACCEPT_ENCODING']))) {
        // Only write the compressed version if it does not yet exist or the
        // original file has changed
        $gzfile = $file . '.gz';
        if (!file_exists($gzfile) || filemtime($gzfile) < $mtime)
            file_put_contents($gzfile, gzencode(file_get_contents($file)));
        // Send compression headers and use the .gz file instead of the
        // original filename
        header('Content-Encoding: gzip');
        $file = $file . '.gz';
    }

    // Vary max-age and expiration headers based on content type
    switch ($content_type) {
        case 'image/gif':
        case 'image/jpeg':
        case 'image/png':
            // Max-age for images: 31 days
            $maxage = 60 * 60 * 24 * 31;
            break;
        default:
            // Max-age for everything else: 7 days
            $maxage = 60 * 60 * 24 * 7;
    }

    // Send remaining headers
    header('Vary: Accept-Encoding');
    header('Cache-Control: max-age=' . $maxage);
    header('Expires: ' . gmdate('D, d M Y H:i:s', time() + $maxage) . ' GMT');
    header('Last-Modified: ' . gmdate('D, d M Y H:i:s', $mtime) . ' GMT');
    header('Content-Type: ' . $content_type);
    header('Content-Length: ' . filesize($file));
    
    // If the request method isn't HEAD, send the file contents
    if ($_SERVER['REQUEST_METHOD'] != 'HEAD') readfile($file);
}

main();

?>

The script is stored as ‚gz.php‘ inside of the root directory of my WordPress installation. It detects if files have changed and recompresses them if needed. In addition it sends a ‚304 Not Modified‘ header if a file hasn’t changed since it was last requested. Furthermore we need to adjust the .htaccess file. For my own WordPress installation it looks like this:

.htaccess

# Set 'Vary' response header for .gz files


Header always append Vary "Accept-Encoding"




ExpiresActive On
ExpiresByType application/json "access plus 1 week"
ExpiresByType application/x-javascript "access plus 1 week"
ExpiresByType application/xml "access plus 1 week"
ExpiresByType image/gif "access plus 1 month"
ExpiresByType image/jpeg "access plus 1 month"
ExpiresByType image/png "access plus 1 month"
ExpiresByType image/x-icon "access plus 1 month"
ExpiresByType text/css "access plus 1 week"
ExpiresByType text/html "access plus 1 week"
ExpiresByType text/plain "access plus 1 week"


# BEGIN WordPress

RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]

# END WordPress

# BEGIN GZIP

# If the user agent accepts gzip encoding...
RewriteCond %{HTTP:Accept-Encoding} gzip
# ...and the requested file exists...
RewriteCond %{REQUEST_FILENAME} -f
# ...then use a PHP script serve a compressed version. Done.
RewriteRule \.(css|html|ico|js|json|txt|xml)$ /gz.php [L]

# END GZIP

For .gz file access, a ‚Vary‘ header is sent to enable correct caching over proxies. Following this directive are several directives for cache retention times (‚Expires‘ and ‚Cache Control‘ header, users may change those as it suits them. In my case, CSS and JS files expire after one week and images after one month.

Alternatively, the mod_rewrite rule for the PHP script can be changed so only the first request calls upon the script, and subsequently the .gz files are accessed directly (which has the drawback that you need to remember to delete any .gz files manually if you make changes, but doesn’t need to call PHP for each file access):


# If the user agent accepts gzip encoding...
RewriteCond %{HTTP:Accept-Encoding} gzip
# ...and if gzip-encoded version of the requested file exists (.gz)...
RewriteCond %{REQUEST_FILENAME}.gz -f
# ...then serve the gzip-encoded file. Done.
RewriteRule ^(.+)$ $1.gz [L]
# Or if the user agent accepts gzip encoding...
RewriteCond %{HTTP:Accept-Encoding} gzip
# ...and the requested file exists...
RewriteCond %{REQUEST_FILENAME} -f
# ...then use a PHP script serve a compressed version. Done.
RewriteRule \.(css|html|ico|js|json|txt|xml)$ /gz.php [L]

Credits: .gz-Icon based on generic package icon from GNOME 2.18 Icon Theme, released under GNU GPL 2.0 Lizenz

This article was published under Attribution-NonCommercial-ShareAlike 3.0 Unported (CC BY-NC-SA 3.0).

Der Beitrag GZIP compression of static assets via mod_rewrite and PHP erschien zuerst bei hoech.net.