title: Warning: Cannot modify header information (PHP LOGIN ERROR)
body: <blockquote>
    <p><strong>Possible Duplicate:</strong><br>
    <a href="https://stackoverflow.com/questions/8028957/headers-already-sent-by-php">Headers already sent by PHP</a>  </p>
  </blockquote>
  
  
  
  <p>I'm trying to set up a simple php username and password login. Everything is working correctly until I try to redirect to the login_success.php page. All information is below please help.</p>
  
  <pre><code>############### Code 
  Warning: Cannot modify header information - headers already sent by (output started at              
  .../edits/admon/minastotian/checklogin.php:4) in    
  .../edits/admon/minastotian/checklogin.php on line 15
  </code></pre>
  
  <p>This is the checklogin.php page. It prints out the error above please help. thank you in advanced.</p>
  
  <pre><code>############### Code
  &lt;?php
      $host="i'm not telling"; // Host name 
      $username="db_user"; // Mysql username 
      $password="db_password"; // Mysql password 
      $db_name="db_name"; // Database name 
      $tbl_name="users"; // Table name
  
      // Connect to server and select databse.
      mysql_connect("$host", "$username", "$password")or die("cannot connect"); 
      mysql_select_db("$db_name")or die("cannot select DB");
  
  
      // username and password sent from form 
      $myusername=$_POST['myusername']; 
      $mypassword=$_POST['mypassword']; 
  
      // To protect MySQL injection (more detail about MySQL injection)
      $myusername = stripslashes($myusername);
      $mypassword = stripslashes($mypassword);
      $myusername = mysql_real_escape_string($myusername);
      $mypassword = mysql_real_escape_string($mypassword);
      $sql="SELECT * FROM $tbl_name WHERE username='$myusername' and     password='$mypassword'";
      $result=mysql_query($sql);
  
      // Mysql_num_row is counting table row
      $count=mysql_num_rows($result);
  
      // If result matched $myusername and $mypassword, table row must be 1 row
      if($count==1){
          // Register $myusername, $mypassword and redirect to file "login_success.php"
          $_SESSION['myusername'] = 'myusername';
          $_SESSION['mypassword'] = 'mypassword';
          header("location:login_success.php");
      }
      else {
          echo "Wrong Username or Password";
      }
  
     ?&gt;
  </code></pre>
  
  <p></p>