php基础教程_php实例
php简介
当前网络技术发展日新月异，各种基于服务端创建动态网站的脚本语言更是层出不穷。其中PHP以其简单、易用、可移植性强等特点，在众多的动态网站语言技术中独树一帜。那么到底什么是PHP，如何使用PHP？本章将来回答这些问题。通过本章的学习，将使读者对PHP有一个大致的了解，并将学会如何把PHP代码加入普通Web页中。
1.1 关于静态网页与动态网页
目前网上的网页有静态网页与动态网页两种形式。在讲这两种网页之前，先了解一下网络构成中的客户机（Client）与服务器（Server）。服务器是安装有服务器软件并且可以向客户机提供诸如网页浏览、数据库查询等服务的设备。而客户机则与之相反，它通过客户端软件如网页浏览器从服务器上获得如网页浏览、软件下载等服务。简单地讲，服务器就是服务提供者，而客户机则是服务获得者。
1.1.1 传统的静态网页HTML
静态网页的实现模式如图所示： 静态网页有以下几个特点：静态网页不能自动更新。静态网页的内容不随浏览用户、浏览时间等条件的变化而变化。静态网页一经发布，无论浏览者浏览与否，它都是实实在在存在的一个文件，都对应一个URL。用静态网页实现人机交互有相当大的局限性。
1.1.2 动态网页与传统网页的区别
与静态网页的实现方法不同，动态网页服务的实现过程如下：客户端向服务器提出申请，服务器根据用户请求，把动态网页内部的代码先在服务器上进行相应的处理，再把生成的结果发送给客户端。其模式如图所示：
1.1.2 动态网页与传统网页的区别
动态网页有以下几个特点：
动态网页在服务器端运行。
不同的人、不同时间、不同地点浏览同一个动态网页，根据代码处理结果不同，会返回不同的内容。
动态网页只有经客户浏览时才会返回一个完整的网页，而其本身并不是一个独立存在于服务器的网页文件。
与静态网页相比，动态网页更容易实现人机交互。
动态网页构建的网站维护起来比静态网页要容易。
1.2 关于PHP
上一节为读者介绍了静态网页与动态网页，而PHP就是动态网页技术中的一种。那么到底什么是PHP，它的发展历史是怎么样的呢？与其他动态网页技术相比，PHP都有些什么特点呢？本节将为读者来解答这些问题。
1.2.1 什么是PHP
早期有人将PHP解释为Personal Home Page，即个人主页。也有人将PHP称作：“PHP：Hypertext Preprocessor”。通俗地说，PHP是一种服务器端、跨平台、可以嵌入HTML的脚本语言。服务器端执行的特性标明了它是动态网页的一种。跨平台，则是指PHP不仅可以运行在Linux系统下同时也可以运行在UNIX或者Windows系统下。另外它还可以很简单地嵌入到普通的HTML页中，用户所要做的只是在普通HTML页中加入PHP代码即可。
1.2.2 PHP的发展历史
PHP最初在1994年由Rasmus Lerdorf进行开发。1995年中期又发布了PHP的第2个版本，定名为PHP/FI（Form Interpreter）。
1997年中开始了第三版的开发计划，开发小组加入了Zeev Suraski及Andi Gutmans，而第三版就定名为PHP 3.0。
2000年5月，PHP 4.0正式发布。它使用了Zend（Zeev+Andi）引擎，提供更高的性能。
2004年7月，PHP 5问世。PHP 5的诞生，使PHP编程进入了一个新时代。Zend II引擎的采用，完备的对象模型、改进的语法设计。终使得PHP成为一个设计完备、真正具有面向对象能力的脚本语言。
1.2.3 PHP与其他CGI程序相比较
同样作为服务端编程语言，PHP与其他CGI程序如ASP.NET、JSP等相比较有其自身的特点，主要表现在以下几个方面：Web服务器支持方面。运行平台的支持。脚本语言不同。数据库支持不同。面向对象的支持不同。
1.3 第一个程序——HELLO WORLD！
<html> <head> <title>HELLO WORLD!</title> </head> <body> <!--以上为普通HTML代码，以下为PHP代码--> <?php echo "HELLO WORLD!"; //用echo打印字符串 ?> <!--以上为PHP代码--> </body> </html>
1.3.1 页面中加入PHP代码
PHP是一种可嵌入的语言。也就是说，它可以很方便地加入到一般常见的HTML页中。用户请求PHP文件时，相关的PHP代码先在服务器端解释执行，生成新的HTML信息，再连同原有的HTML代码一起发送给用户。
1.3.2 PHP页中加入注释
PHP有三种注释：
单行注释：#,//
多行注释：/*some code*/
以上介绍了php基础，php基础教程，了解以上内容是学习php的基础，希望对大家有所帮助。
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