Can someone help me with this error " Warning: Cannot modify header information - headers already sent by"

Question

this is the login form....it says that it cannot modify header information and I tried everything to fix but I cant...can someone help me with my codes..thanks in advance

<?php


       $loginpopup = 'Login Success';
       $failpopup = 'Wrong Username or Password';
          if(!$con)
          {
            die("Error connection" . mysqli_connect_error());

          }
    if (isset($_POST['submitlogin']))
    {

       $login = "SELECT * from admin where username  = '$_POST[user]' AND password ='$_POST[pass]'";

            $getuser = mysqli_query($con,$login) or die(mysql_error());
              while($row = mysqli_fetch_array($getuser))
              {
                if($row==0)
                {
                     echo "<SCRIPT>alert('$failpopup');</SCRIPT>";
                     header("location:index.php");
                }
                else
                {
                  echo "<SCRIPT>alert('$loginpopup');</SCRIPT>";
                  header("location:home.php");
                }
              }
    }
    ?>

display error error_reporting(E_ALL);ini_set('display_errors', 1); — Dave, Jul 18 '16 at 05:07
**WARNING**: Writing your own access control layer is not easy and there are many opportunities to get it severely wrong. This has many dangerous [SQL injection vulnerabilities](http://bobby-tables.com/) since you didn’t [properly escape values](http://bobby-tables.com/php). This code allows *anyone* to get *anything* from your site. **DO NOT** write your own authentication system. Any [development framework](http://codegeekz.com/best-php-frameworks-for-developers/) like [Laravel](http://laravel.com/) comes with an [authentication system](https://laravel.com/docs/5.2/authentication) built-in. — tadman, Jul 18 '16 at 05:08
**WARNING**: At the absolute least follow [recommended security best practices](http://www.phptherightway.com/#security) and never store passwords as plain-text. People who give you their password are trusting that you will store it securely. — tadman, Jul 18 '16 at 05:09
Warning: mysqli_query(): Couldn't fetch mysqli in C:\wamp\www\eserver\index.php on line 200 Call Stack # Time Memory Function Location 1 0.0010 147016 {main}( ) ..\index.php:0 2 0.0730 148464 mysqli_query ( ) ..\index.php:200 — Dan Vincent, Jul 18 '16 at 05:12
SELECT * from admin where username = dan AND password = dan...this is the result of the query($login) sir..can someone fix it thanks.. — Dan Vincent, Jul 18 '16 at 05:57

Ahmad ghoneim · Accepted Answer · 2016-07-18T05:52:14.917

0

if the query failed to run your script will Die because of or die(mysql_error); which won't output anything after $getuser

modify your code to this

 include('movieshub/includes/config.php');
    if ($getuser = mysqli_query($con,$login)) { // check if the query succeeded running
      $count = mysqli_num_rows($getuser);
      if ($count == 0 ) {

             echo "<SCRIPT>alert('$failpopup');</SCRIPT>";
             header("location:index.php");

      } else  {

        while($row = mysqli_fetch_array($getuser)) 
        { //output data }
          echo "<SCRIPT>alert('$loginpopup');</SCRIPT>";
          header("location:home.php");
        }
    }
 } else {
echo "query failed to run";
 }

edited Jul 18 '16 at 05:52

answered Jul 18 '16 at 05:38

Ahmad ghoneim

844
7
13

Warning: mysqli_num_rows() expects parameter 1 to be mysqli_result, boolean given in C:\wamp\www\eserver\index.php on line 204....still an error sir – Dan Vincent Jul 18 '16 at 05:49
that's what we need here – Ahmad ghoneim Jul 18 '16 at 05:54
echo $login; in the last else statement – Ahmad ghoneim Jul 18 '16 at 05:55
SELECT * from admin where username = dan AND password = dan it should be SELECT * from admin where username = 'dan' AND password = 'dan' – Ahmad ghoneim Jul 18 '16 at 05:59
it worked sir thanks...but another error here sir about this header..Warning: Cannot modify header information - headers already sent by (output started at C:\wamp\www\eserver\index.php:165) in C:\wamp\www\eserver\index.php on line 208 – Dan Vincent Jul 18 '16 at 06:09
there must be two session_start() or two header() delete 1 – Ahmad ghoneim Jul 18 '16 at 06:09
okay maybe because you don't have output buffering on put session_start() as the first thing on your php file after the opening tag – Ahmad ghoneim Jul 18 '16 at 06:26
if it didn't work put all your file's code on http://pastebin.com/ and drop the link in the comments here – Ahmad ghoneim Jul 18 '16 at 06:28
ok check this answer please it will help you solve your problemhttp://stackoverflow.com/questions/8028957/how-to-fix-headers-already-sent-error-in-php – Ahmad ghoneim Jul 18 '16 at 06:42
plus in your file you are checking for the connection twice and including connection.php are you sure of that? – Ahmad ghoneim Jul 18 '16 at 06:43
actually it is a trial and error..it really didn't count..I've already deleted it..thanks for the help sir.. – Dan Vincent Jul 18 '16 at 06:48
Hello? @DanVincent – Ahmad ghoneim Jul 18 '16 at 07:19

score 0 · Answer 2 · edited Oct 11 '16 at 04:18

Try the code below:

 <?php

        //if your are using wamp then let $servername,$username and $password be same as below otherwise change them.

        $servername = "localhost"; //insert your severname at the place of localhost
        $username = "root"; //insert your username at the place of root
        $password = "";  //insert your password at the place of ""

        // Create connection
        $con = mysqli_connect($servername, $username, $password); 

        //select database
        mysqli_select_db($con,"test"); //here enter your database name at the place of test

        // Check connection
        if (!$con) {
            die("Connection failed: " . mysqli_connect_error());
        }

       $loginpopup = 'Login Success';
       $failpopup = 'Wrong Username or Password';




    if (isset($_POST['submitlogin']))
    {
        $user=$_POST["user"];
        $pass=$_POST["pass"];

       $login = "SELECT * from admin where username=$user AND password=$pass";

            $getuser = mysqli_query($con,$login);

            $row=mysqli_affected_rows($con);
              if($row>1)
              {
                echo "<SCRIPT>alert('$loginpopup');</SCRIPT>";
                  header("location:home.php");


               }

             else
                {
                  echo "<SCRIPT>alert('$failpopup');</SCRIPT>";
                     header("location:index.php");
                }

    }
    ?>

I've already solved the problem sir and another problem pop out...Warning: Cannot modify header information - headers already sent by (output started at C:\wamp\www\eserver\index.php:166) in C:\wamp\www\eserver\index.php on line 216 — Dan Vincent, Jul 18 '16 at 06:18
when I already successfully logged in and that error will show up — Dan Vincent, Jul 18 '16 at 06:25
just go to your question and you will get the edit option and then update your question there — lazyCoder, Jul 18 '16 at 06:27

Can someone help me with this error " Warning: Cannot modify header information - headers already sent by"

2 Answers2