Warning: Header May Not Contain More Than A Single Header

[phpNOvice]

Hi there, 

i have recieved this notice 

Warning: Header may not contain more than a single header, new line detected in C:\xampp\htdocs\a\Student_Edit_Handler.php on line 53

and these are my codes. Kindly help me to fix this.

<?php
	session_start();
	$session_id = $_SESSION['user_id'];
	if($session_id == null){
	   header("location:Student_Edit.php");
	   die();
	}
	include 'Connect.php';
	$flag = "success";
	function rollbackData(){
		mysql_query(" ROLLBACK ");
		global $flag; 
		$flag = "error";
		if(mysql_error() != null){
			die(mysql_error());
		}
	}
	$student_id = $_POST['student_id'];
	$first_name = $_POST['first_name'];
	$last_name = $_POST['last_name'];
	$gender = $_POST['gender'];
	$date_of_birth = date("Y-m-d",strtotime($_POST['date_of_birth']));
	$contact_no = $_POST['contact_no'];
	$grade = $_POST['grade'];
	$section = $_POST['section'];
	$LRN = $_POST['LRN'];
	$email1 = $_POST['email1'];
	$email2 = $_POST['email2'];
	$address = $_POST['address'];
	$description = $_POST['description'];
	$imagename = "";
	$flag= "";
		mysql_query("SET AUTOCOMMIT = 0 ");
		if(mysql_error() != null){
			die(mysql_error());
		}
	$query = "UPDATE student_information SET first_name='$first_name',last_name='$last_name',";    
	$query .= "gender='$gender',date_of_birth='$date_of_birth',contact_no='$contact_no',grade='$grade',section='$section',";
	$query .= "LRN='$LRN',email1='$email1',email2='$email2',address='$address',description='$description'";     
	$query .= " WHERE student_id='{$_SESSION['user_id']}'";      
	$result = mysql_query($query, $link_id);
	if(mysql_error() != null){
		die(mysql_error());
	}
	if($result)
	{ 
		$flag = "success";
	}
    else
	{
		 $flag = "error"; 
  	}
	header("location:Student_Edit.php?flag=$flag&student_id=student_id=$student_id");
?>
Please advise