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PHP is a widely used Open Source server-side general-purpose scripting language that is especially suited for Web development and can be embedded into HTML. Its syntax draws upon C, Java, and Perl, and is easy to learn. PHP runs on many different platforms and can be used as a standalone executable or as a module under a variety of web servers. It has support for databases, XML, LDAP, IMAP, Java, various Internet protocols, and is extensible via its powerful API.
To denote a file as a PHP files, the extension of the files is .PHP. PHP statements and commands are actually embedded in your HTML documents. When the Web server sees the PHP statements in the Web page, the server executes the statements and sends the resulting output along with the rest of the HTML.