PHP Programming : Code PHP untuk membuang masalah / Remove Exception

"Warning: Cannot modify header information - headers already sent by (output started at" 

Masalah ni selesai apabila saya masukkan code php :

 <?php ob_start(); ?>

Pada permulaan, dan code php :

<?php ob_flush(); ?>

Pada akhir code. Dan segala masalah tersebut selesai.. Terima kasih kepada yang membantu.

PHP Programming : Insert Record

<?php 

require_once('connect.php');

$sql = "INSERT INTO tablename(field1, field2, field3) VALUES ('value1', '$value2', '$value3')";

mysql_query($sql,$connect)or die(mysql_error());

?>

PHP Programming : Display Record From MySQL Database

<?php 
require_once('connect.php');

mysql_select_db($database_connect, $connect);
$query_record = "SELECT * FROM tablename WHERE id = '1'";
$record = mysql_query($query_record, $connect) or die(mysql_error());
$row_record = mysql_fetch_assoc($record);
$totalRows_record = mysql_num_rows($record);

?>

//Display Data
<?php echo $row_record['fieldname']; ?>

PHP Programming : Show Record With BreakLine / Paparkan Rekod Dengan Break Line

<?php 
 echo nl2br("Perkataan disini");
?>

PHP Programming : Identify NULL Field / Kenal pasti field kosong

<?php 
require_once('connect.php');

mysql_select_db($database_connect, $connect);
$query_record = "SELECT * FROM tablename";
$record = mysql_query($query_record, $connect) or die(mysql_error());
$row_record = mysql_fetch_assoc($record);
$totalRows_record = mysql_num_rows($record);

?>

//Display Data
<?php 
if($row_record['fieldname']==NULL)
{
   echo "Field Name Kosong";
}
else
{
   echo $row_record['fieldname'];
}
?>

PHP Programming : Kemaskini Rekod / Update Record

<?php 

require_once('connect.php');

$updatesql = "UPDATE tablename SET field = 'value' WHERE id = '1";
mysql_query($updatesql,$connect)or die(mysql_error());

?>

PHP Programming : Padam Rekod / Delete Record

<?php
require_once('connect.php');

$sql = "DELETE FROM tablename WHERE id='1'";
mysql_query($sql,$connect)or die(mysql_error());
?>