Listing 21-5 shows a simple script that enables output buffering using the ob_start() function, but it also enables gzip-based compression by providing the ob_gzhandler parameter to the ob_start() function. Listing 21-5: compress.php <?php define(MAX, 100); ob_start(“ob_gzhandler”); $output = ‘’; for($i=0;$i<=MAX;$i++) { $output .= “This is line $i <br>”; } echo $output; ?> The following code highlights the extra HTTP headers that are sent when com- pression is enabled: lynx -head -dump http://www.evoknow.com/ch21/gzip/compress.php HTTP/1.1 200 OK Server: Apache/2.0.43 (Unix) PHP/4.1.2 Date: Sat, 07 Dec 2002 20:50:47 GMT Connection: close Content-Encoding: gzip Content-Length: 270 Content-Type: text/html Vary: Accept-Encoding X-Powered-By: PHP/4.1.2 The same script without compression enabled sends the following headers: lynx -head -dump http://www.evoknow.com/ch21/gzip/compress.php HTTP/1.1 200 OK Server: Apache/2.0.43 (Unix) PHP/4.1.2 Date: Sat, 07 Dec 2002 20:52:20 GMT Connection: close Content-Type: text/html X-Powered-By: PHP/4.1.2 726 Part VI: Tuning and Securing PHP Applications 28 549669 ch21.qxd 4/4/03 9:27 AM Page 726 Keep in mind that GZIP is only one practical option in improving your code. Also,the overhead in calling the ZIP function,hit on server RAM, etc.,must be carefully weighed. Caching Your PHP Applications Using the benchmark and compression techniques described in this chapter, you can identify slow code and rewrite it to execute faster if possible. However, another popular method of enhancing the end user’s experience of “speed” is to use caching techniques. By caching the output of your PHP application or caching the genera- tion of PHP opcode, you can achieve higher performance. The following sections discuss these caching techniques in detail. Caching PHP contents using the jpcache cache The jpcache package is a lightweight page caching solution for PHP that reduces server load as PHP-generated pages are cached on the file system or database. It also uses compression (GZIP content-encoding) and ETag-headers, which can result in approximately 80 percent bandwidth savings. When a jpcache-enabled page is requested for the first time, it is run as usual and the generated content is cached in a file or database per the jpcache configura- tion. The cached data is transmitted for any subsequent requests for a configurable amount of time. This means that pages that do not change often on your site can use this caching technique to reduce server load by avoiding running the same script for each request. Configuring jpcache Download the latest jpcache package from http://www.jpcache.com/. Once downloaded, extract the package under your Web server’s document tree. Here is how you configure jpcache for database-based caching: Although you can configure jpcache for file-based caching, file-based caching requires a centralized file system (using NFS or SAMBA) when multi- ple Web servers are serving your contents in a Web server farm. Again, remember the tradeoffs associated with various solutions. For example, although NFS and SAMBA improve caching, their overhead also contributes to slower system functionality. Chapter 21: Speeding Up PHP Applications 727 28 549669 ch21.qxd 4/4/03 9:27 AM Page 727 1. Edit the jpcache.php file to change the $includedir variable to point to the directory in which you have installed jpcache. In the following example, $includedir points to the %DocumentRoot%/ch21/cache/jpcache/ path. // Set the includedir to the jpcache-directory // ORIG: $includedir = “/path/to/jpcache-files”; $includedir = $_SERVER[‘DOCUMENT_ROOT’] . ‘/ch21/cache/jpcache/’; 2. Create a database called jpcache in your MySQL database server. If you want to use an existing database name, skip to the next step. 3. Create a table called CACHEDATA in the jpcache database (or your exist- ing database) using script.sql. For example: mysql -u root -p -D jpcache < script.sql The above command will create CACHEDATA table per script.sql in a data- base called jpcache in localhost. If your MySQL database server is not localhost, you can use -h hostname option. Also, if you are using an exist- ing database replace -D jpcache with -D your_existing_database name. 4. Edit the jpcache-config.php file to include the following lines: $JPCACHE_TYPE = “mysql”; $JPCACHE_TIME = 900; $JPCACHE_DB_HOST = “localhost”; $JPCACHE_DB_DATABASE = “jpcache”; $JPCACHE_DB_USERNAME = “sqluser”; $JPCACHE_DB_PASSWORD = “passwd”; $JPCACHE_DB_TABLE = “CACHEDATA”; $JPCACHE_OPTIMIZE = 1; Here, the cached data will be stored in a table called CACHEDATA in a database called jpcache in the localhost. Access to the database will be allowed using a username called sqluser and the password “passwd”. 5. Now create the following test script called test.php: <?php require “/path/to/jpcache/jpcache.php”; echo time(); phpinfo(); ?> Make sure that /path/to/jpcache in the require() line points to the appropriate directory in which jpcache.php is installed. 728 Part VI: Tuning and Securing PHP Applications 28 549669 ch21.qxd 4/4/03 9:27 AM Page 728 6. Now run this script via a Web browser using http://server/path/ to/jpcache/test.php . You should see a page with a timestamp on top. Keep accessing this script by refreshing the request a few times. Notice that the timestamp shown as the output does not change. This means that caching is working, as the page will be cached for the duration of $JPCACHE_TIME specified in the jpcache-config.php. That’s all that is required to configure jpcache. Now you are ready to use it with your existing PHP applications. Deploying jpcache The jpcache caching should be used only for applications that do not generate their own headers (such as cookies) and are not user-level personalized. You should use this caching technique for pages that generate data from a database or external files unless you are comfortable with the lag that results from non-cache hits. To use jpcache in your existing PHP application, do the following: 1. Edit your application to include the following lines at the very beginning of your PHP application: $cachetimeout=900; require_once($_SERVER[‘DOCUMENT_ROOT’] . ‘/jpcache/jpcache.php’); The preceding code assumes that jpcache is installed in the %DocumentRoot/ jpcache directory. If you install it somewhere else, make sure the path reflects the change. 2. If you wish to cache the output more or less than every 900 seconds, change the value of $cachetimeout. Setting $cachetimeout to -1 will disable caching for the current application. Setting $cachetimeout to 0 will enable a cache that does not expire automatically. Caching PHP contents using the PEAR cache PEAR cache support comes with the PEAR package found at http://pear.php.net. For more information about installing PEAR, refer to Chapter 4. PEAR caching can store cached data in files, shared memory, or a database. Because you are already familiar with jpcache as a database-based caching method, here we will use a file as the cache storage. This section shows you how a simple PHP script (shown in Listing 21-6) can be converted to use the PEAR output caching feature. Chapter 21: Speeding Up PHP Applications 729 28 549669 ch21.qxd 4/4/03 9:27 AM Page 729 Listing 21-6: non_cached.php <?php echo “This is the contents<P>”; echo “Time is “ . date(‘M-d-Y H:i:s A’, time()) . “<BR>”; ?> To use the PEAR output cache for the preceding PHP script, you need to do the following: 1. Include PEAR in the path of this script using the following: $PEAR_DIR = $_SERVER[‘DOCUMENT_ROOT’] . ‘/pear’ ; $PATH = $PEAR_DIR; ini_set( ‘include_path’, ‘:’ . $PATH . ‘:’ . ini_get(‘include_path’)); 2. Include the Output.php cache subclass from PEAR using the following: require_once ‘Cache/Output.php’; 3. Create a cache directory variable as follows: $cacheDir = ‘/tmp/pear_cache’; Make sure this directory is writable by the Web server user. The caching scheme will write cache data in subdirectories within this directory. 4. Create an Output cache object as follows: $cache = new Cache_Output(‘file’, array(‘cache_dir’ => $cacheDir) ); The first argument states that we are choosing file-based caching, and the second argument is an associative array with the cache directory path defined as cache_dir. 5. Generate a unique cache ID for this page as follows: $cache_id = $cache->generateID( array(‘url’ => $REQUEST_URI, ‘post’ => $HTTP_POST_VARS, ‘cookies’ => $HTTP_COOKIE_VARS ) ); 730 Part VI: Tuning and Securing PHP Applications 28 549669 ch21.qxd 4/4/03 9:27 AM Page 730 . “passwd”. 5. Now create the following test script called test .php: < ?php require “/path/to/jpcache/jpcache .php ; echo time(); phpinfo(); ?> Make sure that /path/to/jpcache in the require(). output of your PHP application or caching the genera- tion of PHP opcode, you can achieve higher performance. The following sections discuss these caching techniques in detail. Caching PHP contents. OK Server: Apache/2.0.43 (Unix) PHP/ 4.1.2 Date: Sat, 07 Dec 2002 20:52:20 GMT Connection: close Content-Type: text/html X-Powered-By: PHP/ 4.1.2 726 Part VI: Tuning and Securing PHP Applications 28 549669