This is my code in Participate.php file:
<?php session_start();
$_SESSION['id'] = 'Apps';
?>
<!DOCTYPE html>
<html>
<head>
...
</head>
<body>
...
</body>
</html>
But it shows error:
Warning: PHP Startup: Cannot start session when headers already sent in /Participate.php on line 1
I checked for white spaces there are no any. session_start(); isn't invoking after header. Html section looks fine. File isn't included somewhere, is separated.