PHP+AJAX实时检查帐号是否被注册代码

数据库部分：

CREATE TABLE `username_list` (

  `id` int(11) NOT NULL auto_increment,

  `username` varchar(60) character set latin1 NOT NULL,

  PRIMARY KEY  (`id`)

) ENGINE=MyISAM  DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci AUTO_INCREMENT=1 ;

js代码

 
XML/HTML Code
    输入帐号:                
输入的字符大于等于4才会检测  

check_username.php

include_once("conn.php");  
  
  
  
  
  
//check we have username post var  
  
if(isset($_POST["username"]))  
  
{  
  
    //check if its ajax request, exit script if its not  
  
    if(!isset($_SERVER['HTTP_X_REQUESTED_WITH']) AND strtolower($_SERVER['HTTP_X_REQUESTED_WITH']) != 'xmlhttprequest') {  
  
        die();  
  
    }  
  
      
  
    //trim and lowercase username  
  
    $username =  strtolower(trim($_POST["username"]));   
  
      
  
    //sanitize username  
  
    $username = filter_var($username, FILTER_SANITIZE_STRING, FILTER_FLAG_STRIP_LOW|FILTER_FLAG_STRIP_HIGH);  
  
      
  
    //check username in db  
  
    $results = mysql_query("SELECT id FROM username_list WHERE username='$username'");  
  
      
  
    //return total count  
  
    $username_exist = mysql_num_rows($results); //total records  
  
      
  
    //if value is more than 0, username is not available  
  
    if($username_exist) {  
  
        die('');  
  
    }else{  
  
        die('');  
  
    }  
  
      
  
    //close db connection  
  
      
  
}  
  
?>