PHP+Ajax Detects if an instance tutorial already exists when a user name or message is registered

PHP+Ajax Detecting whether a user name or email already exists at the time of registration is a common and important function in forums or member systems. This paper briefly describes the implementation method of this function in the form of examples. The specific steps are as follows:

1. PHP detection page

The code for the check. php page is as follows:

<script type="text/javascript" src="jiance.js"></script>
<form name="myform" action="" method="get">
  User name: <input name="user" value="" type="text" onblur="funtest100()" />
 <div id="test100"></div>
</form>

2. Ajax validation page

The code for the check. js page is as follows:

var xmlHttp;
function S_xmlhttprequest(){
  if(window.ActiveXobject){
    xmlHttp = new ActiveXObject('Microsoft.XMLHTTP');
  }else if(window.XMLHttpRequest){
    xmlHttp = new XMLHttpRequest();
  }
}
function funtest100(){
  var f = document.getElementsByTagName_r('form')[0].user.value;// Get the contents of the text box 
  S_xmlhttprequest();
  xmlHttp.open("GET","jcfor.php?id="+f,true);// Discovery request 
  xmlHttp.onreadystatechange = byphp;// Ready to execute 
  xmlHttp.send(null);// Send 
}
function byphp(){
  // Judgment state 
  if(xmlHttp.readyState==1){//Ajax Status 
    document.getElementByIdx_x_x('test100').innerHTML = " Loading ";
  }
  if(xmlHttp.readyState==4){//Ajax Status 
    if(xmlHttp.status==200){// Server-side state 
      var bytest100 = xmlHttp.responseText;
      //alert(bytest100);
      document.getElementByIdx_x_x('test100').innerHTML = bytest100; 
    }  
  }
}

3. PHP validation page

The code for the chkfor. php page is as follows:

<?php
 if($_GET[id]){
    sleep(1);
    $conn=mysql_connect('localhost','root','');
    mysql_select_db('test',$conn);
    $sql="SELECT * FROM `user` WHERE `name`='$_GET[id]'";
    $q=mysql_query($sql);
 
    if(is_array(mysql_fetch_row($q))){
      echo " User name already exists "; 
    }else{
      echo " The user name can be used "; 
    }
 }  
?>

I hope the example described in this paper is helpful to the development of PHP program.