PHP isn’t exclusively for Web pages. You can use it like Perl for cron jobs and other tasks.

If PHP is your scripting language of choice when it comes to developing dynamic Web sites, you probably have grown to love its immediacy and power. An estimated ten million Web sites use at least some PHP scripting to generate their pages.

Although most people use PHP primarily as a Web development scripting system, it possesses all the characteristics of a proper general-purpose language that can be useful in a variety of other environments. In this article, I illustrate how it’s possible to use the command-line version of PHP to perform complex shell operations, such as manipulating data files, reading and parsing remote XML documents and scheduling important tasks through cron.

The contents of this article are based on the latest version of PHP at the time of this writing, 4.3.0, which was released at the end of 2002. However, you should be able to use older versions of PHP 4 without many problems. I explain the differences you may encounter as necessary.

PHP-CLI

With the release of PHP 4.3, a new version of the interpreter called command-line interface (or PHP-CLI) is available. PHP-CLI is not a shell as the name implies but, rather, a version of PHP designed to run from the shell. As far as software development is concerned, only a few differences exist between PHP-CLI and its CGI or server API (SAPI) counterparts. For one thing, traditional Apache server variables are not available, as Apache isn’t even in the picture, and the HTTP headers are not output when a script is executed. Also, the engine does not use output buffering, because it would be of no benefit in a non-Web environment.