php登录错误-解析错误：语法错误，意外的T\u IF

我在第23行得到错误，这一行：

if (mysql_num_rows($result) > 0) { 

你能看到我下面的代码，看到我遗漏了什么吗

<?php
// Include database connection and select database UFPProducts
     include "../shopdb/connection.php";
?>
<?php
//
session_start();
// (2) Collect data from form and save in variables

$username=$_POST['username'];
$password=$_POST['password']; 

// (3) Create query of the form below to search the user table
//   "SELECT * FROM Users WHERE UserName='$username' AND  Password='$password'"

"SELECT * FROM USERS where Username='$username' AND Password='$password'"

// (3) Run query through connection

// (4) Check result of query using code below

// if rows found set authenticated user to the user name entered 
if (mysql_num_rows($result) > 0) { 
$_SESSION["authenticatedUser"] = $username;
// Relocate to the logged-in page
header("Location: loggedon.php");
} 
else
// login failed redirect back to login page with error message
{
$_SESSION["message"] = "Could not connect as $username " ;
header("Location: login.php");
}
?>

在末尾放一个分号，然后尝试使用此代码，这样可以最大限度地减少通过SQL注入攻击站点的机会

<?php
// Include database connection and select database UFPProducts
     include "../shopdb/connection.php";
?>
<?php
//
session_start();
// (2) Collect data from form and save in variables

$username=mysql_real_escape_string(htmlentities($_POST['username']));
$password=mysql_real_escape_string(htmlentities($_POST['password']));

// (3) Create query of the form below to search the user table
//   "SELECT * FROM Users WHERE UserName='$username' AND  Password='$password'"

$query = "SELECT * FROM USERS where Username='$username' AND Password='$password'";
$result = mysql_query($query) or die (mysql_error()); 

// (3) Run query through connection

// (4) Check result of query using code below

// if rows found set authenticated user to the user name entered 
if (mysql_num_rows($result) > 0) { 
$_SESSION["authenticatedUser"] = $username;
// Relocate to the logged-in page
header("Location: loggedon.php");
} 
else
// login failed redirect back to login page with error message
{
$_SESSION["message"] = "Could not connect as $username " ;
header("Location: login.php");
}
?>


为什么在您的代码中有“
”从用户名=“$Username”和密码=“$Password”的用户中选择*”
任意浮动？从@Musa开始，我猜您忘了编写查询的其余部分。另外，mysql_*函数已被弃用。请查看mysqli或pdo。刚刚尝试过，我就遇到了以下错误：警告：session_start（）[function.session start]：无法发送会话缓存限制器-头已经发送（/Applications/XAMPP/xamppfiles/htdocs/site/login/loginAction.php，第7行警告：mysql_num_rows（）预期参数1为resource，第23行的/Applications/XAMPP/xamppfiles/htdocs/site/login/loginAction.php中给出的参数为null警告：无法修改标题信息-标题已由（输出开始于/Applications/XAMPP/xamppfiles/htdocs/site/shopdb/connection.php:18）/site/login/loginAction.php在线发送）32@BobUni会话_开始（）；应该在打开php标记之后出现谢谢，我已经这样做了，并得到以下信息：警告：mysql_num_rows（）希望参数1是resource，在第24行的/Applications/XAMPP/xamppfiles/htdocs/site/login/loginAction.php中给出null警告：无法修改头信息-头已经由（输出开始于第33行的/Applications/XAMPP/xamppfiles/htdocs/site/shopdb/connection.php:18）中的/Applications/XAMPP/xamppfiles/htdocs/site/login/loginAction.php如果您遇到上述错误，请尝试将
ob_start（）
在代码的最开始，我的意思是在
之前，比如
之后，你可以把所有的代码放进去，以后再也看不到错误了。如果它对你有用，别忘了投票，否则你可以再问一次。
<?php
// Include database connection and select database UFPProducts
     include "../shopdb/connection.php";
?>
<?php
//
session_start();
// (2) Collect data from form and save in variables

$username=mysql_real_escape_string(htmlentities($_POST['username']));
$password=mysql_real_escape_string(htmlentities($_POST['password']));

// (3) Create query of the form below to search the user table
//   "SELECT * FROM Users WHERE UserName='$username' AND  Password='$password'"

$query = "SELECT * FROM USERS where Username='$username' AND Password='$password'";
$result = mysql_query($query) or die (mysql_error()); 

// (3) Run query through connection

// (4) Check result of query using code below

// if rows found set authenticated user to the user name entered 
if (mysql_num_rows($result) > 0) { 
$_SESSION["authenticatedUser"] = $username;
// Relocate to the logged-in page
header("Location: loggedon.php");
} 
else
// login failed redirect back to login page with error message
{
$_SESSION["message"] = "Could not connect as $username " ;
header("Location: login.php");
}
?>