Tutorial
Login form
by KiNgY | in PHP | posted December 20, 2007
(1 vote) | 542 views
This tutorial should make you understand how a simple login script works
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Thanks KiNgY
PHP:
<?php
session_start();
include("includes/db_connect.php");
?>
The session_start(); function is important and needs to go at the start of each page you want logged in members to access.
The include() function just includes my db_connect script which allows me access to my database.
PHP:
<?php
if($_POST['login']!='') { // tells php what to do if the login button is pressed
// set login variables
$user = mysql_real_escape_string($_POST['user']);
$pass = mysql_real_escape_string($_POST['pass']);
// check critical login data has been submitted
if($user=='' && $pass==''){
$id = "1"; // id number for displaying certain errors
}elseif($user=='') {
$id = "2"; // id number for displaying certain errors
}elseif($pass=='') {
$id = "3"; // id number for displaying certain errors
}else {
// create the deciding data
$query = "SELECT * FROM users WHERE username = '$user' && password = '$pass'";
$result = mysql_query($query);
$decide = mysql_num_rows($result); // brings back the amount of rows with the username and password submitted
// check if data is correct
if($decide=='1') {
$_SESSION['username']="$user"; // sets the session variable username
Header("Location: logged_in.php"); // sends the user to the specified page logged_in.php
exit;
}else {
$id = "5"; // id number for displaying certain errors
}
}
}
?>
This i feel is rather self explanatory, the value of $id depends on which fields of data are missing, i will use $id further down the script to display certain error messages.
If the required data is entered it will be queried against my database and if there is a row with username $user and password $pass the login is a success and the session username is set and the user is forwarded onto a different page in this case logged_in.php.
HTML for the login form
there is also some php in here for displaying error messages
<form action="login.php" method="POST" name="login">
<table border="0" cellspacing="0" cellpadding="0">
<tr>
<td colspan="2" align="center">User Login</td>
</tr>
PHP:
<?php
//this is where the id number comes in to display certain error messages.
if($id>'' && $id<='3'){ echo "<tr><td colspan='2' align='center'>Please fill in missing fields (<span color='red'>*</span>)</td></tr>"; }
if($id=='5'){ echo "<tr><td colspan='2' align='center'>Sorry but your login details where incorrect</td></tr>"; }
?>
<tr>
<td align="left">
PHP:
<?php if($id=='1' || $id=='2'){ echo "<span color='red'>*</span> "; }?>
Username: </td><td><input type="text" name="user"></td>
</tr>
<tr>
<td align="left">
PHP:
<?php if($id=='1' || $id=='3'){ echo "<span color='red'>*</span> "; }?>
Password: </td><td><input type="password" name="pass"></td>
</tr>
<tr>
<td colspan="2" align="center"><input type="submit" name="login" value="login"></td>
</tr>
</table>
</form>
Links
If you would like to see the completed code please visit here:
Full source code
Thanks again KiNgY
