dqyuipw44576 2012-04-28 05:11
浏览 7

我想检查一下用户的存在

Here is the form to have ajax check out user existence.

<!DOCTYPE html>

<html>
    <head><title>Register new user!</title>
    <script src="jquery-1.7.1.min.js"></script>
    </head>
    <body>
        Username:
        <input type="text" name="username" id="username"/><span id="user"></span><br/>
        Password:
        <input type="password" name="password" id="password"/><br/>
        <input type="button" value="Register" name="submit" id="submit" onclick="register_user();"/>
    </body>
    <script>
        function register_user()
        {
            $.ajax(
                {
                    type:"POST",
                    data:username,
                    url:"userexists.php"                    
                })
            .fail(function()
                  {
                    $('#user').html("This user already exists");
                  }
            );                
        }
    </script>
</html>

And here is the userexists.php module

<?php
    // connection to the db
    define(IPHOST,"localhost");
    define(DBPASSWORD,"");
    define(DBUSER,"root");
    define(DATABASE,"ajaxtest");
    define(TABLENAME,"at");

    $conn=mysql_connect(IPHOST,DBUSER,DBPASSWORD) or die(mysql_error());
    mysql_select_db(DATABASE) or die(mysql_error());
    $username=$_POST('username');
    $sql="SELECT username FROM ".TABLENAME." WHERE username=".$username;
    $query=mysql_query($sql);
    if(0!=mysql_numrows($query))
    {
        //
    }
    else
    {

    }
?>

But I am stuck to really figure out how the ajax function actually works, what should I enter the blank field after I know that the entered username has been used, for example ? I don't understand ajax at all.

  • 写回答

1条回答 默认 最新

  • dpka7974 2012-04-28 05:25
    关注

    You need to return a JSON encoded array (look at http://php.net/manual/en/function.json-encode.php). It will essentially return something like this:

    if(0!=mysql_numrows($query))
    {
        echo '{';
        echo '"myMessage":"'.$username." was found'",';
        echo '"myStatus":"1",';
        echo '}';
    }
    else
    {
        echo '{';
        echo '"myMessage":"'.$username." was NOT found'",';
        echo '"myStatus":"0",';
        echo '}';
    }

    Then, your AJAX handles it something like this:

        $.ajax({
        type: "GET",
        url: "userexists.php",
        data: dataString,
        dataType: "json",
        success: function(data) {
            if(data.myStatus== 'Y') {
                var msg = data.myMessage;
            }
        }
    });

    (I realize this is a pretty broad answer, but AJAX calls from PHP using JSON results warrants more than a one paragraph answer for full understanding. There are a lot of good examples if you google jquery AJAX GET JSON results )

    The AJAX Success:/Failure: is whether or not the AJAX call was successful, it has nothing to do with with the called page might return. e.g. Failure will fire if the page you call doesn't exist, or if the code crashes. Your script decides what to return, and the AJAX call must be successful to retrieve whatever that page is sending you.

    评论

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