mysql - Warning: session_start(): Can't send session cache limiter-headers already sent in www\ensure\admin\rpanel.php on line 3 -

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i'm few months old in php , need expert suggestions i'm facing problem while working on project. in advance.

rpanel.php  <?php     if (session_status() == php_session_none)     {         session_start();     }     @ob_start();     $email=$_session['email'];     if(!isset($email))     {         header('location:../index.php');     }     include_once("../include/conn.php"); ?>  note: thete no session_start() function in either index.php or conn.php file 

if have output before session_start() error. check, if have out put before rpane1.php