title: : session_start(): Cannot send session cache limiter - headers already sent (output started at C:\xampp\htdocs\rail\index.php:446) in
body: <p>this is warning. even it is NOT allowing me to open the page admin.php and error is ": </p>
  
  <blockquote>
    <p>Cannot send session cache limiter - headers already sent (output started at C:\xampp\htdocs\rail\index.php:446) in</p>
  </blockquote>
  
  <pre><code>    &lt;?php
  
      ob_start();
  
      error_reporting(E_ALL); 
  </code></pre>
  
  <p><strong>here is warning in this line . where i have started the session</strong></p>
  
  <pre><code>     session_start();
      include("db.php");
      if(isset($_POST['log']))
        {
  
     $user= $_POST['username'];
      $pass= md5($_POST['password']);
  
     $sql=mysql_query( "select * from reg where username= '$user' AND password='$pass' ") or die( mysql_error());
     $data=mysql_num_rows($sql);
        if ($data == 1) {
     while($row = mysql_fetch_array($sql)){ 
  
       $_SESSION['username']=$s1;
     echo '&lt;script&gt;window.location="admin.php"&lt;/script&gt;';
           }
          }
  
  
        else {
          echo '&lt;script type="text/javascript"&gt;';
            echo 'alert("Password Invalid!")';
           echo '&lt;/script&gt;';
  
          }
         }
         ob_end_flush();
         ?&gt;
  </code></pre>
  
  <p><a href="http://i.stack.imgur.com/OFApN.png" rel="nofollow">enter image description here</a></p>