cannot read a session in php

["ITP Vision Promotion" <itpvision@xxxxxxxxx>]

Hello
I have built 21 web sites, when I changed hosting, the PHP log in failed, due to failure to read the php session

to the log in pahe:
@session_start();
if(isset($_POST['user']) && $_POST['user'] != '' && isset($_POST['pass']) && $_POST['pass'] != '')
{
$pass = mysql_escape_string(addslashes($_POST['pass']));
$user = mysql_escape_string(addslashes($_POST['user']));
$query = "select * from table where name = '$user' AND pass = password('$pass') ";
$query2 = mysql_query($query);
	if(mysql_num_rows($query2) < 1)
	{
		header("location:login.php");
		exit;
	}
	else
	{
		$_SESSION['user'] = $user;
		$_SESSION['keylock'] = "abcd";
		header("location:privatepage.php");
		
	}
}
else
{
	
	header("location:$referer");
	exit;

}

I reach the private page, here the session cannot be read , and I am redirected to the forbidden page
@session_start();
if(isset($_SESSION['keylock']) && $_SESSION['keylock'] == "abcd")
{
	$user = $_SESSION['user'] ;
 	$display = "<br><div align = 'center'> Welcome <b> $user </b> 
	
	<a href = 'signout.php'> <b> &raquo; SIGN OUT </b> </a>
	</div> <br> ";
	require_once('header.php');
	echo $display;
}
else
{
	header("location:forbiden.php");
	exit;
}
The second case is true
I tried to comment the redirection, and 
wrote a varaiable
$d = $_SESSION['keylock'] ;
echo " session $d ";
I only get an output session, the session cannot be read