Enabling Gzip Compression of PHP, CSS, and JS Files Without mod_deflate

Normally you can easily enable Gzip compression using mod_deflate by adding the following lines to your .htaccess file:

<IfModule mod_deflate.c>
AddOutputFilterByType DEFLATE text/html text/plain text/xml text/css text/javascript application/javascript application/x-javascript
</IfModule>

But for those of you on shared hosts that don’t allow the mod_deflate module and run PHP in CGI/FastCGI mode you can’t go with the easy method.

So, to serve up your PHP, CSS, and JS files you can try the following method.

Note 1: Your shared web hosting account must support custom php.ini and .htaccess files.

Note 2: Be careful when mixing this solution with other cache/compression applications.

Step 1: PHP Configuration

Add or modify the following lines in your custom php.ini file:

output_handler = Off
zlib.output_compression = On
zlib.output_handler = ob_gzhandler

Now this will take care of gzipping all PHP files.

Step 2: .htaccess Configuration

Add the following lines to the bottom of a .htaccess file in the root of your website.

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteRule ^(.*\.js) gzip.php?type=js&file=$1
RewriteRule ^(.*\.css) gzip.php?type=css&file=$1
</IfModule>

This will redirect all requests for .css and .js files through gzip.php, which we will create in the next step.

Step 3: File Processing PHP Script

The following PHP script will inherently use the PHP compression you’ve already enabled and also add headers to your files take advantage of your client’s browser cache to make subsequent loads faster.

Create a file named gzip.php in your website’s root and add the following lines to it:

<?php
//check that zlib compression is enabled
if(!ini_get('zlib.output_compression')){ die(); }
 
$allowed = array('css','js'); //set array of allowed file types to prevent abuse
 
//check for request variable existence and that file type is allowed
if(isset($_GET['file']) && isset($_GET['type']) && in_array(substr($_GET['file'],strrpos($_GET['file'],'.')+1), $allowed)){
	$data = file_get_contents(dirname(__FILE__).'/'.$_GET['file']); // grab the file contents
 
	$etag = '"'.md5($data).'"'; // generate a file Etag
	header('Etag: '.$etag); // output the Etag in the header
 
	// output the content-type header for each file type
	switch ($_GET['type']) {
		case 'css':
			header ("Content-Type: text/css; charset: UTF-8");
		break;
 
		case 'js':
			header ("Content-Type: text/javascript; charset: UTF-8");
		break;
	}
 
	header('Cache-Control: max-age=300, must-revalidate'); //output the cache-control header
	$offset = 60 * 60;
	$expires = 'Expires: ' . gmdate('D, d M Y H:i:s',time() + $offset) . ' GMT'; // set the expires header to be 1 hour in the future
	header($expires); // output the expires header
 
	// check the Etag the browser already has for the file and only serve the file if it is different
	if ($etag == $_SERVER['HTTP_IF_NONE_MATCH']) {
		header('HTTP/1.1 304 Not Modified');
		header('Content-Length: 0');
	} else {
		echo $data;
	}
}
?>

Great! With these steps in place your css and javascript files will be processed by gzip.php and output using PHP’s gzip compression library (zlib).

This method can be extended to more filetypes by adding to the allowed file types in gzip.php and adding more lines to your .htaccess file.