我不斷收到使用的錯誤消息mysql_num_rows()，您能幫我弄清楚我的代碼出了什么問題嗎？這是我的代碼：<?php //check if the user press submitif (isset($_POST['submit'] )) {    $customer = preg_replace('#[^A-Za-z0-9]#i', '', $_POST["username"]); // filter everything but numbers and letters    $password = preg_replace('#[^A-Za-z0-9]#i', '', $_POST["password"]); // filter everything but numbers and letters    $sql = mysql_query("SELECT id FROM members WHERE username='$customer' AND password='$password' LIMIT 1"); // query the person    // ------- MAKE SURE PERSON EXISTS IN DATABASE ---------    $existCount = mysql_num_rows($sql); // count the row nums    if ($existCount == 1) { // evaluate the count         while($row = mysql_fetch_array($sql)){              $id = $row["id"];         }         $_SESSION["id"] = $id;         $_SESSION["customer"] = $customer;         $_SESSION["password"] = $password;         header("location: index.php");         exit();    } else {        echo 'That information is incorrect, try again <a href="customer_login.php">Click Here</a>';        exit();    }}?>我已經(jīng)mysql_errno()按照您的建議嘗試了..它回顯1146當我搜索該錯誤時說1146: Table 'kossu.nonexistenttable' doesn't exist但是我不知道這意味著什么...請幫助。