PHP 实例 - AJAX 与 XML

AJAX 可用来与 XML 文件进行交互式通信。

AJAX XML 实例

下面的实例将演示网页如何通过 AJAX 从 XML 文件读取信息：

实例

CD info will be listed here...

实例解释 - HTML 页面

当用户在上面的下拉列表中选择某张 CD 时，会执行名为 "showCD()" 的函数。该函数由 "onchange" 事件触发：

<html>
<head>
<script>
function showCD(str)
{
	if (str=="")
	{
		document.getElementById("txtHint").innerHTML="";
		return;
	} 
	if (window.XMLHttpRequest)
	{
		// IE7+, Firefox, Chrome, Opera, Safari 浏览器执行
		xmlhttp=new XMLHttpRequest();
	}
	else
	{
		// IE6, IE5 浏览器执行
		xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
	}
	xmlhttp.onreadystatechange=function()
	{
		if (xmlhttp.readyState==4 && xmlhttp.status==200)
		{
			document.getElementById("txtHint").innerHTML=xmlhttp.responseText;
		}
	}
	xmlhttp.open("GET","getcd.php?q="+str,true);
	xmlhttp.send();
}
</script>
</head>
<body>

<form>
Select a CD:
<select name="cds" onchange="showCD(this.value)">
<option value="">Select a CD:</option>
<option value="Bob Dylan">Bob Dylan</option>
<option value="Bonnie Tyler">Bonnie Tyler</option>
<option value="Dolly Parton">Dolly Parton</option>
</select>
</form>
<div id="txtHint"><b>CD info will be listed here...</b></div>

</body>
</html>

showCD() 函数会执行以下步骤：

检查是否有 CD 被选择
创建 XMLHttpRequest 对象
创建在服务器响应就绪时执行的函数
向服务器上的文件发送请求
请注意添加到 URL 末端的参数（q）（包含下拉列表的内容）

PHP 文件

上面这段通过 JavaScript 调用的服务器页面是名为 "getcd.php" 的 PHP 文件。

PHP 脚本加载 XML 文档，"cd_catalog.xml"：

<?xml version="1.0" encoding="ISO-8859-1"?>
<!-- Edited by XMLSpy® -->
<CATALOG>
	<CD>
		<TITLE>Empire Burlesque</TITLE>
		<ARTIST>Bob Dylan</ARTIST>
		<COUNTRY>USA</COUNTRY>
		<COMPANY>Columbia</COMPANY>
		<PRICE>10.90</PRICE>
		<YEAR>1985</YEAR>
	</CD>
	<CD>
		<TITLE>Hide your heart</TITLE>
		<ARTIST>Bonnie Tyler</ARTIST>
		<COUNTRY>UK</COUNTRY>
		<COMPANY>CBS Records</COMPANY>
		<PRICE>9.90</PRICE>
		<YEAR>1988</YEAR>
	</CD>
	<CD>
		<TITLE>Greatest Hits</TITLE>
		<ARTIST>Dolly Parton</ARTIST>
		<COUNTRY>USA</COUNTRY>
		<COMPANY>RCA</COMPANY>
		<PRICE>9.90</PRICE>
		<YEAR>1982</YEAR>
	</CD>
	<CD>
		<TITLE>Still got the blues</TITLE>
		<ARTIST>Gary Moore</ARTIST>
		<COUNTRY>UK</COUNTRY>
		<COMPANY>Virgin records</COMPANY>
		<PRICE>10.20</PRICE>
		<YEAR>1990</YEAR>
	</CD>
	<CD>
		<TITLE>Eros</TITLE>
		<ARTIST>Eros Ramazzotti</ARTIST>
		<COUNTRY>EU</COUNTRY>
		<COMPANY>BMG</COMPANY>
		<PRICE>9.90</PRICE>
		<YEAR>1997</YEAR>
	</CD>
	<CD>
		<TITLE>One night only</TITLE>
		<ARTIST>Bee Gees</ARTIST>
		<COUNTRY>UK</COUNTRY>
		<COMPANY>Polydor</COMPANY>
		<PRICE>10.90</PRICE>
		<YEAR>1998</YEAR>
	</CD>
	<CD>
		<TITLE>Sylvias Mother</TITLE>
		<ARTIST>Dr.Hook</ARTIST>
		<COUNTRY>UK</COUNTRY>
		<COMPANY>CBS</COMPANY>
		<PRICE>8.10</PRICE>
		<YEAR>1973</YEAR>
	</CD>
	<CD>
		<TITLE>Maggie May</TITLE>
		<ARTIST>Rod Stewart</ARTIST>
		<COUNTRY>UK</COUNTRY>
		<COMPANY>Pickwick</COMPANY>
		<PRICE>8.50</PRICE>
		<YEAR>1990</YEAR>
	</CD>
	<CD>
		<TITLE>Romanza</TITLE>
		<ARTIST>Andrea Bocelli</ARTIST>
		<COUNTRY>EU</COUNTRY>
		<COMPANY>Polydor</COMPANY>
		<PRICE>10.80</PRICE>
		<YEAR>1996</YEAR>
	</CD>
	<CD>
		<TITLE>When a man loves a woman</TITLE>
		<ARTIST>Percy Sledge</ARTIST>
		<COUNTRY>USA</COUNTRY>
		<COMPANY>Atlantic</COMPANY>
		<PRICE>8.70</PRICE>
		<YEAR>1987</YEAR>
	</CD>
	<CD>
		<TITLE>Black angel</TITLE>
		<ARTIST>Savage Rose</ARTIST>
		<COUNTRY>EU</COUNTRY>
		<COMPANY>Mega</COMPANY>
		<PRICE>10.90</PRICE>
		<YEAR>1995</YEAR>
	</CD>
	<CD>
		<TITLE>1999 Grammy Nominees</TITLE>
		<ARTIST>Many</ARTIST>
		<COUNTRY>USA</COUNTRY>
		<COMPANY>Grammy</COMPANY>
		<PRICE>10.20</PRICE>
		<YEAR>1999</YEAR>
	</CD>
	<CD>
		<TITLE>For the good times</TITLE>
		<ARTIST>Kenny Rogers</ARTIST>
		<COUNTRY>UK</COUNTRY>
		<COMPANY>Mucik Master</COMPANY>
		<PRICE>8.70</PRICE>
		<YEAR>1995</YEAR>
	</CD>
	<CD>
		<TITLE>Big Willie style</TITLE>
		<ARTIST>Will Smith</ARTIST>
		<COUNTRY>USA</COUNTRY>
		<COMPANY>Columbia</COMPANY>
		<PRICE>9.90</PRICE>
		<YEAR>1997</YEAR>
	</CD>
	<CD>
		<TITLE>Tupelo Honey</TITLE>
		<ARTIST>Van Morrison</ARTIST>
		<COUNTRY>UK</COUNTRY>
		<COMPANY>Polydor</COMPANY>
		<PRICE>8.20</PRICE>
		<YEAR>1971</YEAR>
	</CD>
	<CD>
		<TITLE>Soulsville</TITLE>
		<ARTIST>Jorn Hoel</ARTIST>
		<COUNTRY>Norway</COUNTRY>
		<COMPANY>WEA</COMPANY>
		<PRICE>7.90</PRICE>
		<YEAR>1996</YEAR>
	</CD>
	<CD>
		<TITLE>The very best of</TITLE>
		<ARTIST>Cat Stevens</ARTIST>
		<COUNTRY>UK</COUNTRY>
		<COMPANY>Island</COMPANY>
		<PRICE>8.90</PRICE>
		<YEAR>1990</YEAR>
	</CD>
	<CD>
		<TITLE>Stop</TITLE>
		<ARTIST>Sam Brown</ARTIST>
		<COUNTRY>UK</COUNTRY>
		<COMPANY>A and M</COMPANY>
		<PRICE>8.90</PRICE>
		<YEAR>1988</YEAR>
	</CD>
	<CD>
		<TITLE>Bridge of Spies</TITLE>
		<ARTIST>T'Pau</ARTIST>
		<COUNTRY>UK</COUNTRY>
		<COMPANY>Siren</COMPANY>
		<PRICE>7.90</PRICE>
		<YEAR>1987</YEAR>
	</CD>
	<CD>
		<TITLE>Private Dancer</TITLE>
		<ARTIST>Tina Turner</ARTIST>
		<COUNTRY>UK</COUNTRY>
		<COMPANY>Capitol</COMPANY>
		<PRICE>8.90</PRICE>
		<YEAR>1983</YEAR>
	</CD>
	<CD>
		<TITLE>Midt om natten</TITLE>
		<ARTIST>Kim Larsen</ARTIST>
		<COUNTRY>EU</COUNTRY>
		<COMPANY>Medley</COMPANY>
		<PRICE>7.80</PRICE>
		<YEAR>1983</YEAR>
	</CD>
	<CD>
		<TITLE>Pavarotti Gala Concert</TITLE>
		<ARTIST>Luciano Pavarotti</ARTIST>
		<COUNTRY>UK</COUNTRY>
		<COMPANY>DECCA</COMPANY>
		<PRICE>9.90</PRICE>
		<YEAR>1991</YEAR>
	</CD>
	<CD>
		<TITLE>The dock of the bay</TITLE>
		<ARTIST>Otis Redding</ARTIST>
		<COUNTRY>USA</COUNTRY>
		<COMPANY>Atlantic</COMPANY>
		<PRICE>7.90</PRICE>
		<YEAR>1987</YEAR>
	</CD>
	<CD>
		<TITLE>Picture book</TITLE>
		<ARTIST>Simply Red</ARTIST>
		<COUNTRY>EU</COUNTRY>
		<COMPANY>Elektra</COMPANY>
		<PRICE>7.20</PRICE>
		<YEAR>1985</YEAR>
	</CD>
	<CD>
		<TITLE>Red</TITLE>
		<ARTIST>The Communards</ARTIST>
		<COUNTRY>UK</COUNTRY>
		<COMPANY>London</COMPANY>
		<PRICE>7.80</PRICE>
		<YEAR>1987</YEAR>
	</CD>
	<CD>
		<TITLE>Unchain my heart</TITLE>
		<ARTIST>Joe Cocker</ARTIST>
		<COUNTRY>USA</COUNTRY>
		<COMPANY>EMI</COMPANY>
		<PRICE>8.20</PRICE>
		<YEAR>1987</YEAR>
	</CD>
</CATALOG>

运行针对 XML 文件的查询，并以 HTML 返回结果：

<?php
$q=$_GET["q"];

$xmlDoc = new DOMDocument();
$xmlDoc->load("cd_catalog.xml");

$x=$xmlDoc->getElementsByTagName('ARTIST');

for ($i=0; $i<=$x->length-1; $i++)
{
	// 处理元素节点
	if ($x->item($i)->nodeType==1)
	{
		if ($x->item($i)->childNodes->item(0)->nodeValue == $q)
		{
			$y=($x->item($i)->parentNode);
		}
	}
}

$cd=($y->childNodes);

for ($i=0;$i<$cd->length;$i++)
{ 
	// 处理元素节点
	if ($cd->item($i)->nodeType==1)
	{
		echo("<b>" . $cd->item($i)->nodeName . ":</b> ");
		echo($cd->item($i)->childNodes->item(0)->nodeValue);
		echo("<br>");
	}
}
?>

当 CD 查询从 JavaScript 发送到 PHP 页面时，将发生：

PHP 创建 XML DOM 对象
查找所有 <artist> 元素中与 JavaScript 所传数据相匹配的名字
输出 album 的信息，并发送回 "txtHint" 占位符

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