php与ajax技术

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>

<?php
    header('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>';
    }
}
?>

<?php
    header('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>