Rasmus Lerdorf - PHP Pocket Reference, 2nd Edition

PHP (PHP Hypertext Preprocessor) is a web scripting language. It wasspecifically designed to solve "the webproblem." PHP is easy to learn because it builds onthe bits and pieces that most people already know. The pieces thatyou don't know are filled in by excellent onlinedocumentation and many high-quality books. This simple approach tosolving the web problem has caught on with an amazing number ofpeople.

This pocket reference further simplifies things by focusing on theabsolute essentials. It provides an overview of the main conceptsneeded for most web applications, followed by quick referencematerial for most of the main PHP functions.

PHP works with many different web servers in many different ways, butby far the most popular way to run PHP is as an Apache module withApache 1.3.x. Full installation instructions for all the differentways to install PHP can be found in the PHP documentation. Here, Icover the Apache module installation.

If you are compiling from the PHP source tarball, follow theinstructions in the INSTALL file found insidethe PHP distribution file. A tarball is a compressed tar file. tar stands fortape archive, but these days it has little to do with tapes. It issimply a way to lump multiple files and directories into a singlefile for distribution. Normally tarballs have the .tar.gz extension to indicate a tar file compressed with gzip . To untar a tarball, use:

On Windows, many utilities (including WinZip) understand tarballs.

If you are installing from a precompiled binary package such as an rpm file, most of the work should be done foryou. But doublecheck that the Apache configuration described below iscorrect.

When you are using PHP as an Apache module, PHP processing istriggered by a special MIME type. This is defined in the Apacheconfiguration file with a line similar to:

This line tells Apache to treat all files that end with the .php extension as PHP files, which means thatany file with that extension is parsed for PHP tags. The actualextension is completely arbitrary and you are free to change it towhatever you wish to use.

If you are running PHP as a dynamic shared object (DSO) module, youalso need this line in your Apache configuration file:

Note that in many default httpd.conf files youwill find AddModule lines. These reallyaren't necessary. They are only needed if you have aClearModuleList directive somewhere in your httpd.conf file. I would suggest simply deletingthe ClearModuleList directive and deleting allyour AddModule lines. The idea behindClearModuleList/AddModule is tomake it possible to reorder already loaded modules in case moduleorder is an issue. With most modules, the order that they areloaded -- which governs the order they are called -- is notimportant. And further, most binary distributions of Apache ship withmost modules compiled as dynamically loadable modules, which meansthat if order is an issue for some reason, you can simply change theorder of the LoadModule calls to fix it.

Don't forget to restart your server after makingchanges to your httpd.conf file. Once the serveris restarted, you can check to see if PHP is working by creating afile in your document root named info.php containing the single line:

Load this up in your browser using http://your.domain.com/info.php . You should seeall sorts of information about PHP. If you don't seeanything, try selecting "ViewSource" in your browser. If you see thephpinfo( ) line, you probably forgot (or mistyped)the AddType line in your httpd.conf file. If the browser tries todownload the file instead, it means that theAddType is there, but the PHP module is not beingtriggered -- perhaps because you forgot theLoadModule line.

Once you have verified that PHP is working, have a look at the PHPinitialization file called php.ini . Thephpinfo( ) page will tell you where PHP isexpecting to find it. PHP functions fine without this file, but withall the default settings. If you want to change the defaults, orperhaps more importantly, you want to be immune from any changes tothe defaults when you upgrade, you should create a php.ini file. The source distribution of PHPcomes with a php.ini-dist file that you canrename and copy into the location specified in the phpinfo() output. The php.ini file itself iswell-commented and self-explanatory for the most part.

You can also put configuration directives inside the Apache httpd.conf file, and, in certain cases, inindividual .htaccess files. This is very usefulfor setting things per-directory or per-virtual host. If you havethis line in the php.ini file:

you can set this in your httpd.conf file with:

There are four httpd.conf directives used forsetting PHP directives: