Getting "Cannot modify header information" from login page

Question

This is probably a duplicate but i am having this issue on login when running the following code

<?php
include('includes/functions.php');

if(isset($_POST['login'])) {
    if(isset($_POST['username'])) {
        if(isset($_POST['password'])) {
            $username = $_POST['username'];
            $query = mysql_query("SELECT * FROM users WHERE Username = '$username'") or die(mysql_error());
            $user = mysql_fetch_array($query);

            if(md5($_POST['password']) == $user['password']); {
                echo 'Login successful';
                $_SESSION['user'] = $user['FullName'];
                header("Location:index.php");
           } 
        } else {
            echo "Please check your password!";
            include('login.php');
        }
    } else {
        echo "Please check your Username!";
        include('login.php');
    }
} else {
    echo "Please check you filled out the login form!";
    include('login.php');
  }
?>

So when username and password are entered i get this output in browser

Login successful
Warning: Cannot modify header information - headers already sent by (output started at /home/site/public_html/admin/dologin.php:12) in /home/site/public_html/admin/dologin.php on line 14

All help will be greatly appreciated

adding this is probably too late but this login worked fine on wamp and is only since i uploaded to a web host — trickyguy08, Jan 27 '15 at 07:59

score 3 · Answer 1 · edited May 23 '17 at 10:26

3

        if(md5($_POST['password']) == $user['password']); {
                                                        ^
            echo 'Login successful';
            $_SESSION['user'] = $user['FullName'];
            header("Location:index.php");
        }

There are 2 issues. That ; inside the if statement should not be there, and then that echo should also go as already mentioned by other answers. Removing the echo should fix that error but your if is messed up because of ; which then causes the header not to work.

Side note: How can I prevent SQL injection in PHP?

edited May 23 '17 at 10:26

Community

1
1

answered Jan 27 '15 at 07:05

Hanky Panky

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yea so with `;` page fails to login but without `;` page goes to dologin.php but doesnt redirect – trickyguy08 Jan 27 '15 at 07:18
The semicolon after the `if` clause ends the if-statement prematurely. It's basically saying: "if the password matches, then execute this empty statement". Then, regardless of the result of the if-statement, the block in the curly-braces gets executed as normal code (not in a conditional). So, you are effectively making the password check succeed in all cases. If login fails without that semicolon, there is probably another issue at play elsewhere in your code (e.g. there is no `else` for the password check, so when it fails, execution continues after all these `if`s). – pieman72 Jan 29 '15 at 00:24

score 1 · Answer 2 · answered Jan 27 '15 at 07:03

1

There should be no output before the header(<..>) so you should get rid of it (remove lines with echo).

answered Jan 27 '15 at 07:03

potashin

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when i remove echo the page doesnt redirect after login – trickyguy08 Jan 27 '15 at 07:04
@trickyguy08 : it redirects, but as you don't `echo` there are no signs of the contrary. You can `echo` , but in the `if` branch, that is not using `header`. – potashin Jan 27 '15 at 07:09
ok i dont need to echo so i have removed it but now page logs in but doesnt redirect – trickyguy08 Jan 27 '15 at 07:14
@trickyguy08 : what about this `;` issue that @Hanky 웃 Panky've pointed out? – potashin Jan 27 '15 at 07:15
yea so with `;` page fails to login with out `;` page goes to dologin.php but doesnt redirect – trickyguy08 Jan 27 '15 at 07:18

score 0 · Answer 3 · answered Jan 27 '15 at 07:03

0

USe :-

<script>location.href - "index.php"; </script>

instead of

header("Location:index.php");

answered Jan 27 '15 at 07:03

Khushboo

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score 0 · Answer 4 · answered Jan 27 '15 at 07:08

0

add ob_start(); at the beginning of file..and remove spaces before and after php tags..

answered Jan 27 '15 at 07:08

Kedar B

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Getting "Cannot modify header information" from login page

4 Answers4