How to convince a potential client?

If you want to use PHP in your company and your manager favours another solution, or if you are trying to convince a potential client that PHP really is a superior choice for the web, you're going to need to have a clear-cut set of reasons why you believe PHP is the superior language. This short list should help you get started:

• PHP is cross-platform. It can run on Windows, Linux, BSD, Mac OS X, and Solaris, as well as a variety of other platforms.
• PHP is free. You can download the source code, use it, and even make changes to it without ever having to pay any licensing costs. You can even give away your own modified version of PHP.
• PHP is fast. In the majority of scripts beyond basic benchmarks, PHP will easily compete with both Perl and Python, and usually match Microsoft's ASP.NET. Add to that the fact that PHP code can be cached for execution, and PHP's performance is first-class.
• PHP is capable and reliable. There are thousands of pre-written functions to perform a wide variety of helpful tasks - handling databases of all sorts (MySQL, Oracle, MS SQL, PostgreSQL, and many others), file uploads, FTP, email, graphical interfaces, generating Flash movies, and more. It is already running on millions of servers around the world making it reliable in most demanding situations
• PHP is extendable. Writing your own extension to PHP is a common and easy way to implement speed-critical functionality, and PHP's extension API is a particularly rich and flexible system.
• PHP is easy to debug. There are a number of debuggers, both commercial and freeware, that make debugging PHP a snap.
• PHP is advancing. With the release of PHP 5, PHP has introduced features that have long been waited for, including more comprehensive error handling, better object orientation, and, of course, more speed.

The base of the PHP language is very simple, having just enough to set and retrieve variables, work with loops, and check whether a statement is true or not. The real power behind PHP comes with its extensions - add-ons to the base language that give it more flexibility. There are hundreds of extensions to PHP, and they can be broken down into five distinct types: core, bundled, PECL, third party, and DIY.

• Core extensions are extensions that are bundled with PHP itself, and enabled by default. For all intents and purposes they are part of the base language, because, unless you explicitly disable them (few people do, and sometimes you cannot), they are available inside PHP. For example, the mechanism to handle reading and saving files in PHP is actually handled by an extension that is automatically compiled into PHP.
• Bundled extensions are extensions that are bundled with PHP, but not enabled by default. These are commonly used, which is why they are bundled, but they are not available to you unless you specifically enable them. For example, the mechanism to handle graphics creation and editing is handled by an extension that is bundled with PHP, but not enabled by default.
• PECL(pronounced "pickle") stands for "PHP Extension Community Library", and is as a subset of the PHP Extension and Application Repository, PEAR.
• Third-party extensions are written by programmers who wanted to solve a particular problem that was unsolvable without them creating a new extension. There is a variety of third-party extensions available out there.
• Finally, Do-It-Yourself (DIY) extensions are simply extensions you created yourself. PHP has a remarkably rich extension creation system that makes it quite simple to add your own code as long as you know C.