用于验证用户名是否可用的php ajax实现代码

//var poststr = "act=reply&bookid="+bookid+"&book_content="+ book_content;

//type:post or get

function send_request(http_request,url,poststr) {

// 确定发送请求的方式和url以及是否同步执行下段代码

http_request.open("post", url, true);

http_request.setrequestheader("content-type","application/x-www-form-urlencoded");

http_request.send(poststr);

}

function create_obj(){

var http_request = false;

//开始初始化xmlhttprequest对象

if(window.xmlhttprequest) { //mozilla 浏览器

http_request = new xmlhttprequest();

if (http_request.overridemimetype) {//设置mime类别

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) { // 异常，创建对象实例失败

return false;

}

return http_request;

}

function getcheck(){

var http_request = create_obj();

http_request.onreadystatechange = function(){

if (http_request.readystate == 4) {

if (http_request.status == 200) {

var http_result2 = http_request.responsetext;

if('该登录名可以使用'==http_result2){

cancel_popup_win('username',true);

username_check = true;

}else{

popup_win('username',http_result2);

username_check = false;

}

}

}

}

var username=document.getelementbyid('username').value;

var poststr = "act=check&userid="+ username;

send_request(http_request,"http://www.3ppt.com",poststr);

}

</script>

<li>

<span class="dlm"><em>设置登录名：</em>

<input tabindex="1" class="text_2" name="username"
id="username" value="" type="text" maxlength="16" autocomplete="off"
onblur="getcheck();"/>登录名:4-16/怪字符/全数字/无内容/下划线/有全角/有空格/有大写/有汉字<
/span>

</li>