PHP+MySQL: Simple login script won't work

weasel8 · December 23, 2008

I'm getting an odd error with a simple user login script I'm writing. Towards the beginning the script checks for $_POST['submit'] to see if the form has been filled out and submitted and needs to be processed.

But I keep seeing this error when I access the script in my browser:

Notice: Undefined index: submit in /srv/http/bm/index.php on line 4

Here's the script, index.php.

<?php
require("header.php");

if ($_POST['submit']) {
$sql = "SELECT * FROM users WHERE username = " . $_POST['username'] . " and password = " . $_POST['password']; 
$res = mysql_query($sql) or die(mysql_error());
$num = mysql_num_rows($res); 
if ($res == 1) {
	// log in user...
}
else {
	$error = 1;  
}
}
?>

<h1>exmeamente.ws/bm</h1>
<p>Dead simple online bookmarks<br />
(<a href="about.html">more, for the curious</a>)</p>
<?php 
if (isset($error)) {
	echo "<p>Typo somewhere... have another go.</p>"; 
}
?>
<p><form action="index.php" method="post">
	<table>
		<tr>
			<td>Username</td>
			<td><input type="text" name="username" /></td>
		</tr>
		<tr>
			<td>Password</td>
			<td><input type="text" name="password" /></td>
		</tr>
		<tr>
			<td></td>
			<td><input type="submit" value="Log in" name="submit" /> or <a href="register.php">make one</a></td>
		</tr>
	</table>
</form></p>


<?
require("footer.php"); 
?>

Here's header.php and config.php, just in case.

<?php
require("config.php"); 
?>
<html>
<head>
<title><?php echo $config_sitename; ?></title>
<link rel="stylesheet" href="stylesheet.css" />
</head>
<body>

<?php

$dbhost = "localhost"; 
$dbuser = "root"; 
$dbpassword = "[removed]"; 
$dbdatabase = "bm"; 

$db = mysql_connect($dbhost, $dbuser, $dbpassword) or die(mysql_error()); 
mysql_select_db($dbdatabase) or die("Unable to select database");

$config_sitename = "exmeamente.ws/bm";

?>

Additionally, when I try to use the form, say with username "sampleusername" and password "samplepassword", I get THIS error and nothing else:

sampleusernameUnknown column 'sampleusername' in 'where clause'

I've been over the scripts a thousand times and I still can't figure out what's wrong. Can better versed in PHP + MySQL identify my problems?

EDIT: I also just remembered this, for what it's worth: I consistently get the following error from phpMyAdmin, but haven't fixed it because according to php.net I need to recompile PHP with a certain flag to make it work, and so far it seems to have not broken anything.

Cannot load mcrypt extension. Please check your PHP configuration.

ngreenwood6 · December 23, 2008

If you don't have register_globals turned on then you will get that error try changing this:

if ($_POST['submit']) {

to this:

$submit = $_POST['submit'];
if($submit){

EDIT:

As for this:

sampleusernameUnknown column 'sampleusername' in 'where clause'

Same thing you need to define them first like this:

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

\\then change the query to this:
$sql = "SELECT * FROM users WHERE username = '$username' AND password = '$password'";

weasel8 · December 23, 2008

Thanks, now I understand why I got the error. I'm used to Ubuntu's distribution of PHP, which is different from the one I'm using. The solution you offered didn't work (I got the same error), so I created a second file to process the form, login.php. It seems to be working pretty well, but now I get yet another error.

With login.php, I can easily print $_POST['username'] and $_POST['password'], but when I try to plug them into an SQL query, I get this:

Unknown column 'sampleuser' in 'where clause'

I've gone over my query and I can't figure out what I've done wrong. Here's login.php.

<?php
require("header.php");

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

if ($submit) {
	echo $username;
	echo $password; 	
	$sql = "SELECT * FROM users WHERE username = $username and password = $password;"; 
	$res = mysql_query($sql) or die(mysql_error());
	if ($res == 1) {
		// log in user...
		echo "You have been logged in."; 
	}
	else {
		$error = 1;  
	}
}
require("footer.php"); 
?>

Anyone see what's the problem?

fenway · December 23, 2008

You're missing single quotes around your string literals in your query string.

ngreenwood6 · December 23, 2008

try this:

<?php
require("header.php");

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

if ($submit) {
	echo $username;
	echo $password; 	
	$sql = "SELECT * FROM users WHERE username = '$username' and password = '$password'"; 
	$res = mysql_query($sql) or die(mysql_error());
	if ($res == 1) {
		// log in user...
		echo "You have been logged in."; 
	}
	else {
		$error = 1;  
	}
}
require("footer.php"); 
?>

You were missing the single quotes and you had a semi-colon after password which was not needed

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PHP+MySQL: Simple login script won't work

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