<!DOCTYPE html>
<html lang="en"><head> <meta charset="UTF-8"> <title>Document</title></head><body> <input type="text" id="username"><span id="show"></span> <script> function $(id){ return document.getElementById(id); } var username=$("username"); var show=$("show"); var http=new XMLHttpRequest; username.οnblur=function(){ http.open("GET","a.php?username="+this.value,true); http.send(); } http.onreadystatechange=function(){ if(this.readyState==4 && this.status==200){ if(this.responseText=="0"){ show.innerHTML="ok"; } else{ show.innerHTML="error"; } } } </script></body></html>
php:
<?php
if($_GET["username"]){//定义用户名 $a=$_GET["username"];//用户名赋给$a if($a=="admin"){//判断接受的用户名是否是admin echo "0"; //正确返回1 } else{ echo "1";//不是返回0 } }?>