Quick Start Tutorial for XML

<p><br></p> <h2>Chapter 1 What is XML? Quick introduction to XML</h2> <h3>1. What is XML? First, let's take a look at a piece of code </h3> <p><strong>XML</strong> (Extensible Markup Language) </p> <pre class="brush:php;toolbar:false"><?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE class [ <!ELEMENT class ANY>     <!ELEMENT person (name,time,msg,data)>     <!ELEMENT name (#PCDATA)>     <!ELEMENT time (#PCDATA)>     <!ELEMENT msg (#PCDATA)>     <!ELEMENT data (#PCDATA)> ]> <class>     <person>         <name>0x584A</name>         <time>2015年9月25日 10:24:41</time>         <msg>holle,world!</msg>         <!--这里是CDATA区间-->         <data><![CDATA[<XML的那些事...> -> 跟随0x584A、学习XML.. ]]></data>     </person> </class></pre> <p> Let's take a look at the specific display effect after running in the browser: </p> <p class="image-package"><img src="https://img.php.cn/upload/article/000/000/164/729e3f29ba6f560af48f387edc5ab46c-0.png" alt="Quick Start Tutorial for XML" ><br></p> <p class="image-caption">1.png</p> <h3>2.What is XML mainly used for? </h3> <p> I believe that students who have been online for a long time have seen files with the suffix <strong>.xml</strong>. This is what we call <strong>XML</strong> files. <br>First after <strong>HTML</strong> became popular, the <strong><a href="http://www.php.cn/wiki/1550.html" target="_blank">W3C</a></strong> organization felt that the limitations of the HTML language were too great, so it introduced XML for the purpose of <strong> Replace HTML language </strong>. </p> <p>Of course, it seems that W3C’s plan has not been successful. <code>(However, there are no eggs⊙﹏⊙)</code></p> <p>Although <strong>XML</strong> has not replaced <strong>HTML</strong>, its unique characteristics allow it to continue to this day. . </p> <pre class="brush:php;toolbar:false">优点： 1. 高度自定义[标签] 2. 不同语言中的数据流通规范 3. XML是用来描述数据的。而在HTML中，数据是写在HTML标签中的。 4. XML设计是用来描述数据的：重点是什么是数据，怎么存放数据。而HTML则是用来显示数据：重点是怎么显示数据，及怎么更好的显示数据。</pre> <p>Explain XML in one sentence: <code>XML is a cross-platform, software- and hardware-independent tool for processing information (a tool for data manipulation and data transmission)</code></p> <blockquote> <p>Um.. Let me share a joke with you: </p> <p>Q: When should I use XML? </p> <p>Answer: You can write in your resume that you know XML..</p> </blockquote> <h3>3. Quick introduction to XML</h3> <p>Based on the first piece of code above , let us analyze it step by step. </p> <pre class="brush:php;toolbar:false"><?xml version="1.0" encoding="UTF-8"?></pre> <p>The first one is to declare first, declare that this XML version is <strong>1.0</strong>, and use <strong>UTF-8</strong><a href="http://www.php.cn/code/225.html" target="_blank">character set</a> to identify it . </p> <p>The following code is used for <a href="http://www.php.cn/wiki/1528.html" target="_blank">DTD</a><a href="http://www.php.cn/code/12132.html" target="_blank">constraints</a>. </p> <pre class="brush:php;toolbar:false"><!-- 内部 DOCTYPE 声明 定义文档是class类型文件 --> <!DOCTYPE class [ <!-- 元素class 通过类别关键字ANY声明元素，可包含任何可解析的数据组合 -->     <!ELEMENT class ANY>     <!-- 定义person元素内有四个元素 注意：约束顺序也是节点顺序 -->     <!ELEMENT person (name,time,msg,data)>     <!-- 定义name元素 为#PCDATA类型 -->     <!ELEMENT name (#PCDATA)>     <!ELEMENT time (#PCDATA)>     <!ELEMENT msg (#PCDATA)>     <!ELEMENT data (#PCDATA)> ]></pre> <p> Then someone asked: </p> <p><strong>What is DTD? </strong></p> <p>Let’s take a look at the explanation on W3C: </p> <blockquote><p><strong>Document type definition (DTD) can define legal XML document building blocks. It uses a series of legal elements to define the structure of the document. </strong></p></blockquote> <p>Uh... <code>(Actually, it's just bullshit, it's the same as not saying it...)</code></p> <p>Okay, no more complaining. In fact, it sets restrictions on the XML elements, <a href="http://www.php.cn/wiki/169.html" target="_blank"> attributes</a>, etc. we write. The structure we write must follow DTD constraints. </p> <hr> <p>Let us continue to look at the following code: </p> <pre class="brush:php;toolbar:false"><class>     <person>         <name>0x584A</name>         <time>2015年9月25日 10:24:41</time>         <msg>holle,world!</msg>         <!--这里是CDATA区间-->         <data><![CDATA[<XML的那些事...> -> 跟随0x584A、学习XML.. ]]></data>     </person> </class></pre> <p>Did you find anything? </p> <p>Yes, yes, it is a tree structure. Let's take a look at the DTD constraint. The root node <strong>class</strong> is first defined, and then the <strong>person</strong> element is defined and there are four elements inside the <br><strong>person</strong> element. Elements <strong>name</strong>, <strong>time</strong>, <strong>msg</strong>, <strong>data</strong>. </p> <p>There is a strange thing among them, we call it <code>CDATA section</code>, only the text in the section will be ignored by the parser, so it <a href="http://www.php.cn/php/php-tp-sameoutput.html" target="_blank">outputs it as is</a>Special symbols<code><</code>、<code>></code>, etc...</p> <pre class="brush:php;toolbar:false">好了、至此关于XML的快速入门结束了，你学会了多少呢？ 下一章让我们来学习XML的语法、元素及属性吧 o(∩_∩)o</pre> <p>       </p>

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