计算行时出错

Question

我正在登录，我在计算MySQL查询的行数时遇到错误。错误如下。

 Warning: mysql_num_rows() expects parameter 1 to be resource, boolean given in /home/nzcraftn/public_html/bs/login.php on line 13

Warning: Cannot modify header information - headers already sent by (output started at /home/nzcraftn/public_html/bs/login.php:13) in /home/nzcraftn/public_html/bs/login.php on line 21

我正在使用此代码进行登录。

<?php
session_start();
include('config.php');

$user = protect($_POST['username']);
$pass = protect($_POST['password']);

$salt = "a123b123";
$thepass = md5($salt.md5($pass));

$res = mysql_query("SELECT `username`,`password` WHERE (`username` = '$user' AND `password` = '$thepass')");

$count = mysql_num_rows($res);

if($count == 1) {
$_SESSION['user'] = $user;
print($_SESSION['user']);
//header('Location: /panel/index.php');
} else {
$_SESSION['errormsg'] = "<div style='color: #FF0000'>Invalid Login!</div>";
header('Location: index.php');
}
?>

Answer 1

您的陈述中有错误，因此mysql_query正在返回false。请在代码中添加错误检查（以及记录调试）。

（您的SELECT缺少FROM条款。）

Answer 2

通过自己在MySQL提示符中运行SQL查询，确保SQL查询正常工作。在SQL查询周围添加一些故障排除代码，如下所示：

$query = 'SELECT ...';
$res = mysql_query($query) or die(mysql_error()."\n".$query);