plz find the error
it give this error
Warning: Cannot modify header information - headers already sent by (output started at D:\xampp\htdocs\soomrof\a_task_2_1.php:3) in D:\xampp\htdocs\soomrof\a_task_2_1.php on line 24
<?
include("connection.php");
$check=false;
$sql=mysql_query("select * from doctor_schedule_information where doctor_ID='".$_POST[doctor_id]."'") or die(mysql_error());
if(mysql_num_rows($sql)==1)
{
$row=mysql_fetch_array($sql);
$check=true;
}
else
{
$check=false;
}
if($check==true)
{
header("location:a_task_2_3.php");
}
else
{
header("location:a_task_2.php");
}
?>