php $_POST 不起作用。“注意：未定义索引：用户名...”
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$_POST not working. "Notice: Undefined index: username..."
提问by blacblu
Possible Duplicate:
PHP: “Notice: Undefined variable” and “Notice: Undefined index”
So, I am currently learning PHP and was reading on a book about the md5 function for passwords, so I decided to give it a try and see how it goes. I also decided to use the POST method rather than the GET, since I saw people saying that it is safer and doesn't let the variables appearing on the URL.
所以，我目前正在学习 PHP 并且正在阅读一本关于密码的 md5 函数的书，所以我决定尝试一下，看看它是如何进行的。我还决定使用 POST 方法而不是 GET，因为我看到人们说它更安全并且不会让变量出现在 URL 上。
For my testing project I made a very simple form, which follows:
对于我的测试项目，我制作了一个非常简单的表格，如下所示：
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title></title>
</head>
<body>
<form action="dologin" method="POST">
<table border="0">
<tbody>
<tr>
<td>Username:</td>
<td><input type="text" name="username"></td>
</tr>
<tr>
<td>Password:</td>
<td><input type="password" name="password"></td>
</tr>
</tbody>
</table>
<input type="submit" value="Login">
</form>
</body>
</html>
The problem is that when I enter the values on BOTH fields and click "Login" I get the following output on the other PHP file.
问题是，当我在两个字段中输入值并单击“登录”时，我在另一个 PHP 文件中得到以下输出。
Notice: Undefined index: username in C:\xampp\htdocs\md5\home\dologin\index.php on line 11
Username non existent
Here follows the code for the "/dologin/index.php" file
下面是“/dologin/index.php”文件的代码
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title></title>
</head>
<body>
<?php
mysql_connect("localhost", "root") or die(mysql_error());
mysql_select_db("test") or die(mysql_error());
$query = "SELECT password FROM users WHERE username='".$_POST['username']."'";
$result = mysql_query($query);
$row = mysql_num_rows($result);
if(isset($row)){
$password = (mysql_result($result,$row - 1));
$enteredpassword = md5("w@#$@#".$_GET['password']."^#3f%#^");
if($password == $enteredpassword){
if(!isset($_COOKIE['PHPSESSID'])){
session_start();
}
$_SERVER['LOGIN_STATUS'] = true;
} else {
die("Access denied");
}
} else {
die("Username non existent");
}
?>
</body>
</html>
Any help at all on my issue is very much appreciated, thank you for reading.
非常感谢您对我的问题的任何帮助，感谢您的阅读。
回答by Josh Brody
undefined indexmeans that somewhere in the $_POST array, there isn't an index (key) for the key username.
未定义索引意味着 $_POST 数组中的某处，没有键username的索引（键）。
You should be setting your posted values into variables for a more clean solution, and it's a good habit to get into.
您应该将发布的值设置为变量以获得更干净的解决方案，这是一个好习惯。
If I was having a similar error, I'd do something like this:
如果我有类似的错误，我会做这样的事情：
$username = $_POST['username']; // you should really do some more logic to see if it's set first
echo $username;
If username didn't turn up, that'd mean I was screwing up somewhere. You can also,
如果用户名没有出现，那意味着我在某个地方搞砸了。你也可以，
var_dump($_POST);
To see what you're posting. var_dump is really useful as far as debugging. Check it out: var_dump
要查看您发布的内容。var_dump 在调试方面非常有用。检查一下：var_dump
回答by marvin
first of all,
首先，
be sure that there is a post
确定有帖子
if(isset($_POST['username'])) {
// check if the username has been set
}
second, and most importantly, sanitize the data, meaning that
其次，也是最重要的，清理数据，这意味着
$query = "SELECT password FROM users WHERE username='".$_POST['username']."'";
is deadly dangerous, instead use
是致命的危险，而是使用
$query = "SELECT password FROM users WHERE username='".mysql_real_escape_string($_POST['username'])."'";
and please research the subject sql injection
并请研究主题sql 注入
回答by silent_coder14
You should check if the POST['username']is defined. Use this above:
您应该检查是否POST['username']已定义。使用上面这个：
$username = "";
if(isset($_POST['username'])){
$username = $_POST['username'];
}
"SELECT password FROM users WHERE username='".$username."'"
