PHP 独特的语法混合了 C、Java、Perl 以及 PHP 自创新的语法。它可以比 CGI 或者 Perl 更快速的执行动态网页。用PHP做出的动态页面与其他的编程语言相比，PHP是将程序嵌入到HTML文档中去执行，执行效率比完全生成HTML标记的CGI要高许多；PHP还可以执行编译后代码，编译可以达到加密和优化代码运行，使代码运行更快。PHP具有非常强大的功能，所有的CGI的功能PHP都能实现，而且支持几乎所有流行的数据库以及操作系统。
PHP5在长时间的开发及多个预发布版本后，2004年7月13日，PHP5.0发布。该版本以Zend引擎Ⅱ为引擎，并且加入了新功能如PHP Date Objects（PDO）。现在PHP5.0版本强化更多的功能。首先，完全实现面向对象，提供名为PHP兼容模式的功能。其次是XML功能，PHP5.0版本支持可直观地访问XML数据、名为SimpleXML的XML处理用界面。同时还强化了XML ">Web服务支持，而且标准支持SOAP扩展模块。数据库方面，PHP新版本提供旨在访问MySOL的新界面——MySQL。除此前的界面外，还可以使用面向对象界面和预处理语句（Prepared Statement）等MySQL的新功能．另外，PHP5.0上还捆绑有小容量RDBMS-SQLite．
The PHP development team would like to announce the immediate availability of PHP 5.3.6. This release focuses on improving the stability of the PHP 5.3.x branch with over 60 bug fixes, some of which are security related.
Security Enhancements and Fixes in PHP 5.3.6:
·Enforce security in the fastcgi protocol parsing with fpm SAPI.
·Fixed bug #54247 (format-string vulnerability on Phar). (CVE-2011-1153)
·Fixed bug #54193 (Integer overflow in shmop_read()). (CVE-2011-1092)
·Fixed bug #54055 (buffer overrun with high values for precision ini setting).
·Fixed bug #54002 (crash on crafted tag in exif). (CVE-2011-0708)
·Fixed bug #53885 (ZipArchive segfault with FL_UNCHANGED on empty archive). (CVE-2011-0421)
Key enhancements in PHP 5.3.6 include:
·Upgraded bundled Sqlite3 to version 3.7.4.
·Upgraded bundled PCRE to version 8.11.
·Added ability to connect to HTTPS sites through proxy with basic authentication using stream_context/http/header/Proxy-Authorization.
·Added options to debug backtrace functions.
·Changed default value of ini directive serialize_precision from 100 to 17.
·Fixed Bug #53971 (isset() and empty() produce apparently spurious runtime error).
·Fixed Bug #53958 (Closures can't 'use' shared variables by value and by reference).
·Fixed bug #53577 (Regression introduced in 5.3.4 in open_basedir with a trailing forward slash).
·Over 60 other bug fixes.
Windows users: please mind that we do no longer provide builds created with Visual Studio C++ 6. It is impossible to maintain a high quality and safe build of PHP for Windows using this unmaintained compiler.
For Apache SAPIs (php5_apache2_2.dll), be sure that you use a Visual Studio C++ 9 version of Apache. We recommend the Apache builds as provided by ApacheLounge. For any other SAPI (CLI, FastCGI via mod_fcgi, FastCGI with IIS or other FastCGI capable server), everything works as before. Third party extension providers must rebuild their extensions to make them compatible and loadable with the Visual Studio C++9 builds that we now provide.
All PHP users should note that the PHP 5.2 series is NOT supported anymore. All users are strongly encouraged to upgrade to PHP 5.3.6.
下载地址：
PHP 5.3.6 (tar.bz2) [10,695Kb] - 17 March 2011
md5: 2286f5a82a6e8397955a0025c1c2ad98 PHP 5.3.6 (tar.gz) [14,032Kb] - 17 March 2011
md5: 88a2b00047bc5
3afbbbdf10ebe28a57e
Windows下载地址：http://windows.php.net/download/