我正在尝试建立一个捐赠中心，使用的是Totorialzine的源代码。

到目前为止，到目前为止一切都对我来说还算不错，但是我一直在苦苦挣扎并试图研究一整天的唯一问题，无法确切知道代码的实际错误所在

这是我的访客捐赠时在页面上提交评论时得到的。

Fatal error: Call to undefined function mb_strlen() in /home/yoursn0w/public_html/livetv/premium/thankyou.php on line 14

这是php文件中的代码。

<?php

require "config.php";
require "connect.php";

if(isset($_POST['submitform']) && isset($_POST['txn_id']))
{
    $_POST['nameField'] = esc($_POST['nameField']);
    $_POST['websiteField'] =  esc($_POST['websiteField']);
    $_POST['messageField'] = esc($_POST['messageField']);

    $error = array();

    if(mb_strlen($_POST['nameField'],"utf-8")<2)
    {
        $error[] = 'Please fill in a valid name.';
    }

    if(mb_strlen($_POST['messageField'],"utf-8")<2)
    {
        $error[] = 'Please fill in a longer message.';
    }

    if(!validateURL($_POST['websiteField']))
    {
        $error[] = 'The URL you entered is invalid.';
    }

    $errorString = '';
    if(count($error))
    {
        $errorString = join('<br />',$error);
    }
    else
    {
        mysql_query("   INSERT INTO dc_comments (transaction_id, name, url, message)
                        VALUES (
                            '".esc($_POST['txn_id'])."',
                            '".$_POST['nameField']."',
                            '".$_POST['websiteField']."',
                            '".$_POST['messageField']."'
                        )");

        if(mysql_affected_rows($link)==1)
        {
            $messageString = '<a href="donate.php">You were added to our donor list! &raquo;</a>';
        }
    }
}

?>

我的phpMyAdmin数据库已完成上传

这是我按照安装说明进行操作的地方

http://tutorialzine.com/2010/05/donation-center-php-mysql-paypal-
api/