PHP is a computer scripting language, originally designed for producing dynamic web pages. It is used mainly in server-side-scripting. But can be used from a command line interface or in standalone graphical applications. PHP is currently the most popular apache module among all servers using Apache as a web server. Among all currently existing computer programming languages, it is considered the fourth most popular, ranked only behind java, c,and visual basic. PHP is a widely-used general-purpose scripting language that is especially suited for web development and can be embedded into HTML.PHP generally runs on a web server, taking PHP code as its input and creating Web pages as output. However, it can also be used for command-line scripting and client side GUI applications. PHP can be deployed on most web servers and almost every operating system and platform free of charges. The PHP Group also provides the complete source code for users to build, customize and extend for their own use. Originally designed to create dynamic web pages, PHP’s principal focus is server-side-scripting While running the PHP parser with a web server and web browser, the PHP model can be compared to other server-side scripting languages such as Microsoft’s ASP.NET system.
PHP only parses code within its delimiters. Anything outside its delimiters is sent directly to the output and not parsed by PHP. PHP supports a number of different delimiters. The most common delimiters are <?php and?>, respectively open and close delimiters. <script language=”php”> </script> style delimiters are also always available, so these two forms are the most portable. Short tags (<? or <?= and?>) are also quite commonly used, but are along with ASP style tags less portable, as they can be disabled in the PHP configuration. For this reason the use of Short tags and ASP style tags is discouraged. The purpose of these delimiters is to separate PHP code from non-PHP code (notably HTML). Note that the delimiters are required to process PHP statements. Everything outside the delimiters is ignored by the parser and is simply passed through as output.
