正在检查用户联机状态

Question

我想检查用户的在线状态，并根据我阅读的许多来源构建了一个页面。我仍然不能得到想要的结果。也许有人可以查看我当前的代码，让我知道这个部分出了什么问题？下面的代码是检查用户在线状态的代码，我目前也收到以下错误消息：

Fatal error: Call to undefined method PDOStatement::prepare() in C:xampphtdocsincludesonline_status.php on line 11

<?php 
error_reporting(E_ALL & ~E_NOTICE);
require_once($_SERVER['DOCUMENT_ROOT'] . '/includes/dbconfig.php');
$timestamp = date("Y-m-d H:i:s");

#RETURN A LIST OF WHICH USERS ARE INDICATED AS ONLINE IN THE TABLE 
            $stmtonline = $db->prepare('SELECT * FROM sys_members'); 
            $stmtonline->execute;   
            $foundRows = $stmtonline->prepare("SELECT FOUND_ROWS()")->fetchColumn();            
    if($foundRows->rowCount())
        {
        echo $foundRows->rowCount();
        }

if($row_count=="0")
        {

#INSERT THE USER INTO THE ONLINE_USERS TABLE IF THEY DO NOT EXIST
            $stmtinsrt = $db->prepare('INSERT INTO sys_online_users (memberID, username, last_active) VALUES (:memberID, :username, :last_active)');
            $stmtinsrt->execute(array(
                ':memberID' => $_SESSION['memberID'],
                ':username' => $_SESSION['username'],
                ':last_active' => $timestamp                
            ));
            $id = $db->lastInsertId('memberID');
        }
        else 
        {
#UPDATE THE USER'S CURRENT STATUS IN THE TABLE IF THE DO EXIST
            $stmtupd = $db->prepare('INSERT INTO sys_online_users (memberID, username, last_active) VALUES (:memberID, :username, :last_active)');
            $stmtupd->execute(array(
                ':memberID' => $_SESSION['memberID'],
                ':username' => $_SESSION['username'],
                ':last_active' => $timestamp                
            ));
            $id = $db->lastInsertId('memberID');
        }   


?>

Answer 1

将$stmtonline->prepare替换为$db->prepare

Answer 2

通过简化查询，我最终使其工作起来。。以下是对我有效的结果：

<?php error_reporting(E_ALL & ~E_NOTICE);     require_once($_SERVER['DOCUMENT_ROOT'] . '/includes/dbconfig.php');    $timestamp = date("Y-m-d H:i:s");
    {

        $stmtinsrt = $db->prepare('INSERT INTO sys_page_hit (memberID, username, last_active) VALUES (:memberID, :username, :last_active) ON DUPLICATE KEY UPDATE last_active= :last_active');
        $stmtinsrt->execute(array(
            ':memberID' => $_SESSION['memberID'],
            ':username' => $_SESSION['username'],
            ':last_active' => $timestamp                
        ));
        $id = $db->lastInsertId('memberID');
    }

？>