web2.0的到来，ajax逐渐成为主流，什么是ajax，ajax的开发模式，优点，使用技术。（ajax概述，ajax使用的技术，需要注意的 问题，在PHP应用ajax技术的应用）

什么是ajax，ajax的开发模式，优点。

ajax是由jesse james garrett创建的，是asynchronous javascript and xml，异步javascript和xml技术，ajax并不是一门新的语言或技术，它是javascript，xml，css，dom等多种技术的组合，可以实现客户端的异步请求操作，可以在不刷新页面下与服务器进行通信，从而减少了用户的等待时间。

ajax开发模式：
浏览器（客户端） http传输，http请求， web服务器 数据存储，后端处理，继承系统，服务器端。

客户端（浏览器）JavaScript调用，ajax引擎 http请求，http传输， web和xml服务器，数据存储，后端处理，继承系统（服务端）。

优点：减轻服务器的负担，可以把部分由服务器负担的工作转移到客户端上，无刷新更新页面，可以调用xml等外部数据，基于标准化的并被广泛支持的技术。

JavaScript是一种在web页面中添加动态脚本代码的解释性程序语言。

xmlhttprequest

ie浏览器把xmlhttp

var http_request = new ActiveXObject("Msxml2.XMLHTTP");

var http_request = new ActiveXObject("Microsoft.XMLHTTP");

mozailla,safari等其他浏览器

var http_request = new XMLHttpRequest();

if(window.XMLHttpRequest){
http_request = new XMLHttpRequest();
}else if(window.ActiveXObject){ try{ http_request = new ActiveXObject("Msxml2.XMLHTTP"); }catch(e){ try{ http_request = new ActiveXObject("Msxml2.XMLHTTP"); }catch(e){ try{ http_request = new ActiveXObject("Microsoft.XMLHTTP"); }catch(e){} } }

XMLHttpRequest对象的常用方法：

open()方法用于设置进行异步请求目标的url

open("method", "url" [,asyncFlag [,"userName" [, "password"]]])

send()方法用于向服务器发送请求

send(content)

setRequestHeader()方法

setRequestHeader()方法为请求的http头设置值

setRequestHeader("label","value")

label用于指定http头，value用于指定http头设置值

open()方法过后才能使用setRequestHeader()方法

abort()方法
abort()方法用于停止当前异步请求

getAllResponseHeaders()方法
getAllResponseHeaders()方法用于以字符串形式完整的http头信息。

xmlhttpRequest对象常用的属性
onreadystatechange 每个状态改变时都会触发这个事件处理器，通常会调用一个JavaScript函数。

readyState 请求的状态：

0 为未初始化
1 为正在下载
2 为已加载
3 在交互中
4 为完成

responseText 服务器的响应，表示字符串

responseXML 服务器的响应，表示xml

status 返回服务器的http状态码
statusText 返回http状态码对应的文本

xml语言为可扩展的标记语言，提供了用于描述结构化数据的格式。xmlHttpRequest对象与服务器交换的数据，通常采用xml格式。

dom为文档对象模型，为xml文档的解析定义了一组接口。

在PHP中应用AJAX技术检测用户名

<script language="javascript"> var http_request = false; function createRequest(url) { //初始化对象并发出XMLHttpRequest请求 http_request = false; if (window.XMLHttpRequest) { //Mozilla等其他浏览器 http_request = new XMLHttpRequest(); if (http_request.overrideMimeType) { http_request.overrideMimeType("text/xml"); } } else if (window.ActiveXObject) { //IE浏览器 try { http_request = new ActiveXObject("Msxml2.XMLHTTP"); } catch (e) { try { http_request = new ActiveXObject("Microsoft.XMLHTTP"); } catch (e) {} } } if (!http_request) { alert("不能创建XMLHTTP实例!"); return false; } http_request.onreadystatechange = alertContents; //指定响应方法 http_request.open("GET", url, true); //发出HTTP请求 http_request.send(null); } function alertContents() { //处理服务器返回的信息 if (http_request.readyState == 4) { if (http_request.status == 200) { alert(http_request.responseText); } else { alert('您请求的页面发现错误'); } } } </script> <script language="javascript"> function checkName() { var username = form1.username.value; if(username=="") { window.alert("请填写用户名!"); form1.username.focus(); return false; } else { createRequest('checkname.php?username='+username+'&nocache='+new Date().getTime()); } } </script>

<?phpheader('Content-type: text/html;charset=GB2312');       //指定发送数据的编码格式为GB2312$link=mysql_connect("localhost","root","root"); mysql_select_db("db_database",$link); $GB2312string=iconv( 'UTF-8', 'gb2312//IGNORE' , $RequestAjaxString); //Ajax中先用encodeURIComponent对要提交的中文进行编码 mysql_query("set names gb2312"); $username=$_GET[username]; $sql=mysql_query("select * from tb_user where name='".$username."'"); $info=mysql_fetch_array($sql); if ($info){ echo "很报歉!用户名[".$username."]已经被注册!"; }else{ echo "祝贺您!用户名[".$username."]没有被注册!"; } ?>

类别添加

<script language="javascript"> var http_request = false; function createRequest(url) { //初始化对象并发出XMLHttpRequest请求 http_request = false; if (window.XMLHttpRequest) { //Mozilla等其他浏览器 http_request = new XMLHttpRequest(); if (http_request.overrideMimeType) { http_request.overrideMimeType("text/xml"); } } else if (window.ActiveXObject) { //IE浏览器 try { http_request = new ActiveXObject("Msxml2.XMLHTTP"); } catch (e) { try { http_request = new ActiveXObject("Microsoft.XMLHTTP"); } catch (e) {} } } if (!http_request) { alert("不能创建XMLHTTP实例!"); return false; } http_request.onreadystatechange = alertContents; //指定响应方法 http_request.open("GET", url, true); //发出HTTP请求 http_request.send(null); } function alertContents() { //处理服务器返回的信息 if (http_request.readyState == 4) { if (http_request.status == 200) { sort_id.innerHTML=http_request.responseText; //设置sort_id HTML文本替换的元素内容 } else { alert('您请求的页面发现错误'); } } } </script> <script language="javascript"> function checksort() { var txt_sort = form1.txt_sort.value; if(txt_sort=="") { window.alert("请填写文章类别!"); form1.txt_sort.focus(); return false; } else { createRequest('checksort.php?txt_sort='+txt_sort); } } </script>

<?php$link=mysql_connect("localhost","root","root"); mysql_select_db("db_database",$link); $GB2312string=iconv( 'UTF-8', 'gb2312//IGNORE',$RequestAjaxString); //Ajax中先用encodeURIComponent对要提交的中文进行编码 mysql_query("set names gb2312"); $sort=$_GET[txt_sort]; mysql_query("insert into tb_sort(sort) values('$sort')"); header('Content-type: text/html;charset=GB2312'); //指定发送数据的编码格式为GB2312 ?> <table border="0" cellpadding="0" cellspacing="0"> <tr> <td> <select name="select" > <?php $link=mysql_connect("localhost","root","root"); mysql_select_db("db_database23",$link); $GB2312string=iconv( 'UTF-8', 'gb2312//IGNORE' , $RequestAjaxString); //Ajax中先用encodeURIComponent对要提交的中文进行编码 mysql_query("set names gb2312"); $sql=mysql_query("select distinct * from tb_sort group by sort"); $result=mysql_fetch_object($sql); do{ header('Content-type: text/html;charset=GB2312'); //指定发送数据的编码格式为GB2312 ?> <option value="<?php echo $result->sort;?>" selected><?php echo $result->sort;?></option> <?php }while($result=mysql_fetch_object($sql)); ?> </select>

xml基础技术

了解xml，使用simpleXML解析文档的方法
遍历xml文档，修改，保存xml，创建xml文档的方法

xml语法
xml文档结构，xml声明，处理指令，注解，xml元素，xml属性，使用cdata标记，xml命令空间。

XML文档结构

<?xml version="1.0" encoding="gb2312" standalone="yes"?>

<?xml-stylesheet type="text/css" href="111.css"?>

XML声明

<?xml version="1.0" encoding="gb2312" standalone="yes"?>

处理指令

<?xml-stylesheet type = "text/css" href="111.css"?>

<?处理指令名 处理执行信息?>

xml-stylesheet：样式表单处理指令
type="text/css"：设定了文档所使用的样式是css
href="111.css"：设定了样式文件的地址

XML属性

<标签 属性名="属性值" 属性名=""…>内容</标签＞

SimpleXML
创建SimpleXML对象
Simplexml_load_file()函数，将指定的文件解析到内存中
Simplexml_load_string()函数，将创建的字符串解析到内存当中
Simplexml_load_date()函数，将一个使用dom函数创建的domDocument对象导入到内存当中

遍历所有子元素
children()方法和foreach循环语句可以遍历所有子节点元素

遍历所有属性
SimpleXML对象中的attributes()方法

<?xml version="1.0" encoding="GB2312"?> <exam> </exam>

<?php
header('Content-Type:text/html;charset=utf-8');
?><?php
/* 第一种方法 */ $xml_1 = simplexml_load_file("5.xml"); print_r($xml_1); /* 第二种方法 */ $str = <<<XML <?xml version='1.0' encoding='gb2312'?> <Object> <ComputerBook> <title>PHP</title> </ComputerBook> </Object> XML; $xml_2 = simplexml_load_string($str); echo '<br>'; print_r($xml_2); /* 第三种方法 */ $dom = new domDocument(); $dom -> loadXML($str); $xml_3 = simplexml_import_dom($dom); echo '<br>'; print_r($xml_3); ?>

<?php
header('Content-Type:text/html;charset=utf-8');
?>
<style type="text/css"><?php $str = <<<XML <?xml version='1.0' encoding='gb2312'?> <object> <book> <computerbook>PHP</computerbook> </book> <book> <computerbook>PHP</computerbook> </book> </object> XML; $xml = simplexml_load_string($str); foreach($xml->children() as $layer_one){ print_r($layer_one); echo '<br>'; foreach($layer_one->children() as $layer_two){ print_r($layer_two); echo '<br>'; } } ?>

<?php
$str = <<<XML
<?xml version='1.0' encoding='gb2312'?>
<object name='commodity'><book type='computerbook'><bookname name='22'/></book><book type='historybook'><booknanme name='111'/></book>
</object>
XML;
$xml = simplexml_load_string($str);
foreach($xml->children() as $layer_one){foreach($layer_one->attributes() as $name => $vl){ echo $name.'::'.$vl; } echo '<br>'; foreach($layer_one->children() as $layer_two){ foreach($layer_two->attributes() as $nm => $vl){ echo $nm."::".$vl; } echo '<br>'; } } ?>

<?phpheader('Content-Type:text/html;charset=utf-8');
?><?php
$str = <<<XML <?xml version='1.0' encoding='gb2312'?> <object name='商品'> <book> <computerbook>P123</computerbook> </book> <book> <computerbook name='456'/> </book> </object> XML; $xml = simplexml_load_string($str); echo $xml[name].'<br>'; echo $xml->book[0]->computerbook.'<br>'; echo $xml->book[1]->computerbook['name'].'<br>'; ?>

<?php
header('Content-Type:text/html;charset=utf-8');
$str=<<<XML
<?xml version='1.0' encoding='gb2312'?>
<object name='商品'><book><computerbook type='12356'>123</computerbook></book>
</object>
XML;$xml = simplexml_load_string($str);
echo $xml[name].'<br />'; $xml->book->computerbook['type'] = iconv('gb2312','utf-8','PHP123'); $xml->book->computerbook = iconv('gb2312','utf-8','PHP456'); echo $xml->book->computerbook['type'].' => '; echo $xml->book->computerbook; ?>

<?php
$xml = simplexml_load_file('10.xml');
$xml->book->computerbook['type'] = iconv('gb2312','utf-8','PHP1'); $xml->book->computerbook = iconv('gb2312','utf-8','PHP2'); $modi = $xml->asXML(); file_put_contents('10.xml',$modi); $str = file_get_contents('10.xml'); echo $str; ?>

<?php//Message_XML类，继承PHP5的DomDocument类class Message_XML extends DomDocument{ //属性 private $Root; //方法 //构造函数 public function __construct() { parent:: __construct(); //创建或读取存储留言信息的XML文档message.xml if (!file_exists("message.xml")){ $xmlstr = "<?xml version='1.0' encoding='GB2312'?><message></message>"; $this->loadXML($xmlstr); $this->save("message.xml"); } else $this->load("message.xml"); } public function add_message($user,$address){ //添加数据 $Root = $this->documentElement; //获取留言消息 $admin_id =date("Ynjhis"); $Node_admin_id= $this->createElement("admin_id"); $text= $this->createTextNode(iconv("GB2312","UTF-8",$admin_id)); $Node_admin_id->appendChild($text); $Node_user = $this->createElement("user"); $text = $this->createTextNode(iconv("GB2312","UTF-8",$user)); $Node_user->appendChild($text); $Node_address = $this->createElement("address"); $text= $this->createTextNode(iconv("GB2312","UTF-8",$address)); $Node_address->appendChild($text); $Node_Record = $this->createElement("record"); $Node_Record->appendChild($Node_admin_id); $Node_Record->appendChild($Node_user); $Node_Record->appendChild($Node_address); //加入到根结点下 $Root->appendChild($Node_Record); $this->save("message.xml"); echo "<script>alert('添加成功');location.href='".$_SERVER['PHP_SELF']."'</script>"; } public function delete_message($admin_id){ //删除数据 $Root = $this->documentElement; $xpath = new DOMXPath($this); $Node_Record= $xpath->query("//record[admin_id='$admin_id']"); $Root->removeChild($Node_Record->item(0)); $this->save("message.xml"); echo "<script>alert('删除成功');location.href='".$_SERVER['PHP_SELF']."'</script>"; } public function show_message(){ //读取数据 $root=$this-documentElement; $xpath=new DOMXPath($this); $Node_Record=$this->getElementsByTagName("record"); $Node_Record_length=$Node_Record->length; print"<table width='506' bgcolor='#FFFFCC'><tr>"; print"<td width='106' height='22' align='center'>"; print"<b>用户名</b>"; print"</td><td width='400' align='center'>"; print"<b>留言信息</b></td></tr>"; for($i=0;$i<$Node_Record->length;$i++){ $k=0; foreach($Node_Record->item($i)->childNodes as $articles){ $field[$k]=iconv("UTF-8","GB2312",$articles->textContent); $k++; } print"<table width='506' bgcolor='#FFFFCC'><tr>"; print"<td width='100' height='22' align='center'>"; print"$field[1]"; print"</td><td width='300' align='left'>"; print"$field[2]"; print"</td><td width='100' align='center'>"; print"<a href='?Action=delete_message&admin_id=$field[0]'>删除</a></td>"; print"</tr></table>"; }} public function post_message(){ print "<table width='506' bgcolor='#FFFFCC'><form method='post' action='?Action=add_message'>"; print "<tr><td width='106'height='22'>&nbsp;&nbsp;&nbsp;&nbsp;用户名：</td><td><input type=text name='user' size=50></td></tr>"; print "<tr><td width='106' height='22'>&nbsp;&nbsp;&nbsp;&nbsp;留言信息：</td><td width='400'><textarea name='address' cols='48' rows='5' id='address'></textarea></td></tr>"; print "<tr><td width='106' height='30'>&nbsp;&nbsp;<input type='submit' value='添加数据'></td><td align='right'><a href=?Action=show_message>查看数据</a>&nbsp;&nbsp;&nbsp;&nbsp;</td></tr></form></table>"; } } ?> <html> <head> <title>定义一个PHP读取XML类</title> <style> td,body{font-size:12px} a:link { text-decoration: none; } a:visited { text-decoration: none; } a:hover { text-decoration: none; } a:active { text-decoration: none; } </style> <meta http-equiv="Content-Type" content="text/html; charset=gb2312"></head> <body> <table width=506 height=50 border=0 cellpadding=0 cellspacing=0 bgcolor="#33BE6B"> <tr> <td width="506" height=50 valign="bottom" background="title.gif"><table width="506"> <tr> <td height="24" align="right" scope="col">&nbsp;&nbsp;<a href=?Action=post_message>添加数据</a>&nbsp;&nbsp;&nbsp;</td> </tr> </table></td> </tr> <?php $HawkXML = new Message_XML; $Action =""; if(isset($_GET['Action'])) $Action = $_GET['Action']; switch($Action){ case "show_message": //查看 $HawkXML->show_message(); break; case "post_message": //提交 $HawkXML->post_message(); break; case "add_message": //添加 $HawkXML->add_message($_POST['user'],$_POST['address']); break; case "delete_message": //删除 $HawkXML->delete_message($_GET['admin_id']); break; } ?> </table> </body> </html> 

<?php//Message_XML类，继承PHP5的DomDocument类class Message_XML extends DomDocument{ //属性 private $Root; //方法 //构造函数 public function __construct() { parent:: __construct(); //创建或读取存储留言信息的XML文档message.xml if (!file_exists("message.xml")){ $xmlstr = "<?xml version='1.0' encoding='GB2312'?><message></message>"; $this->loadXML($xmlstr); $this->save("message.xml"); } else $this->load("message.xml"); } public function add_message($user,$address){ //添加数据 $Root = $this->documentElement; //获取留言消息 $admin_id =date("Ynjhis"); $Node_admin_id= $this->createElement("admin_id"); $text= $this->createTextNode(iconv("GB2312","UTF-8",$admin_id)); $Node_admin_id->appendChild($text); $Node_user = $this->createElement("user"); $text = $this->createTextNode(iconv("GB2312","UTF-8",$user)); $Node_user->appendChild($text); $Node_address = $this->createElement("address"); $text= $this->createTextNode(iconv("GB2312","UTF-8",$address)); $Node_address->appendChild($text); $Node_Record = $this->createElement("record"); $Node_Record->appendChild($Node_admin_id); $Node_Record->appendChild($Node_user); $Node_Record->appendChild($Node_address); //加入到根结点下 $Root->appendChild($Node_Record); $this->save("message.xml"); echo "<script>alert('添加成功');location.href='".$_SERVER['PHP_SELF']."'</script>"; } public function show_message(){ //读取数据 $root=$this-documentElement; $xpath=new DOMXPath($this); $Node_Record=$this->getElementsByTagName("record"); $Node_Record_length=$Node_Record->length; print"<table width='506' bgcolor='#FFFFCC'><tr>"; print"<td width='106' height='22' align='center'>"; print"<b>用户名</b>"; print"</td><td width='400' align='center'>"; print"<b>留言信息</b></td></tr>"; for($i=0;$i<$Node_Record->length;$i++){ $k=0; foreach($Node_Record->item($i)->childNodes as $articles){ $field[$k]=iconv("UTF-8","GB2312",$articles->textContent); $k++; } print"<table width='506' bgcolor='#FFFFCC'><tr>"; print"<td width='100' height='22' align='center'>"; print"$field[1]"; print"</td><td width='400' align='left'>"; print"$field[2]"; print"</td>"; print"</tr></table>"; }} public function post_message(){ print "<table width='506' bgcolor='#FFFFCC'><form method='post' action='?Action=add_message'>"; print "<tr><td width='106'height='22'>&nbsp;&nbsp;&nbsp;&nbsp;用户名：</td><td><input type=text name='user' size=50></td></tr>"; print "<tr><td width='106' height='22'>&nbsp;&nbsp;&nbsp;&nbsp;留言信息：</td><td width='400'><textarea name='address' cols='48' rows='5' id='address'></textarea></td></tr>"; print "<tr><td width='106' height='30'>&nbsp;&nbsp;<input type='submit' value='添加数据'></td><td align='right'><a href=?Action=show_message>查看数据</a>&nbsp;&nbsp;&nbsp;&nbsp;</td></tr></form></table>"; } } ?> <html> <head> <title>使用XML来存储少量的数据</title> <style> td,body{font-size:12px} a:link { text-decoration: none; } a:visited { text-decoration: none; } a:hover { text-decoration: none; } a:active { text-decoration: none; } </style> <meta http-equiv="Content-Type" content="text/html; charset=gb2312"></head> <body> <table width=506 height=50 border=0 cellpadding=0 cellspacing=0 bgcolor="#33BE6B"> <tr> <td width="506" height=50 valign="bottom" background="title.gif"><table width="506"> <tr> <td height="24" align="right" scope="col">&nbsp;&nbsp;<a href=?Action=post_message>添加数据</a>&nbsp;&nbsp;&nbsp;</td> </tr> </table></td> </tr> <?php $HawkXML = new Message_XML; $Action =""; if(isset($_GET['Action'])) $Action = $_GET['Action']; switch($Action){ case "show_message": //查看 $HawkXML->show_message(); break; case "post_message": //提交 $HawkXML->post_message(); break; case "add_message": //添加 $HawkXML->add_message($_POST['user'],$_POST['address']); break; } ?> </table> </body> </html>