ทำ Date diff เทียบข้อมูลจาก DB มัน Fatal error: Cannot redeclare datediff()

<?php
	 function DateDiff($strDate1,$strDate2)
	 {
				return (strtotime($strDate2) - strtotime($strDate1))/  ( 60 * 60 * 24 );  // 1 day = 60*60*24
	 }
	 function TimeDiff($strTime1,$strTime2)
	 {
				return (strtotime($strTime2) - strtotime($strTime1))/  ( 60 * 60 ); // 1 Hour =  60*60
	 }
	 function DateTimeDiff($strDateTime1,$strDateTime2)
	 {
				return (strtotime($strDateTime2) - strtotime($strDateTime1))/  ( 60 * 60 ); // 1 Hour =  60*60
	 }

	 echo "Date Diff = ".DateDiff("2008-08-01","2008-08-31")."<br>";
	 echo "Time Diff = ".TimeDiff("00:00","19:00")."<br>";
	 echo "Date Time Diff = ".DateTimeDiff("2008-08-01 00:00","2008-08-01 19:00")."<br>";
?>

<?php  include('connect.php');
$i = date("Y-m-d");              
$sql = " select * from tb_movie order by m_date_in DESC";
$query = mysql_query($sql);
$cols = 0;
$auto=1;
	$c = $cols;
function DateDiff($i,$x) <<<ตัวปห ^^ 
 	 {
    	return (strtotime($x) - strtotime($i))/  ( 60 * 60 * 24 );  // 1 day = 60*60*24
 	}
 
while($db= mysql_fetch_array($query))
                {

	 $x = $db[m_date_in];

	
	if(DateDiff($i,$x)<=0)
	{
		if($auto<6)
{
	$auto++;
			$c--;	
             ?>
                <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
                <td width="" align="center" valign="top"><table width="105" border="0" cellspacing="0" cellpadding="0">
                  <tr>
                    <td width="105" height="118" align="center" valign="middle" class="hovergallery"><img src="<?php echo $db[m_iposter] ?>" width="128" height="178" border="0" title="<?php  echo $db[m_name_en]; ?>" /></td>
                  </tr>
                  <tr>
                    <td width="105" height="30" align="center" valign="top"><a href="<?php echo "movie_room.php?m_id=".$db[m_id].""; ?>" target="_blank"><img src="img/etc/watch_trailer.png" width="128" height="25" border="0" /></a></td>
                  </tr>
                  <tr>
                    <td align="center"><a href="<?php echo "movie_room.php?m_id=".$db[m_id].""; ?>" target="_blank">
                      <?php  echo $db[m_name_short]; ?>
                    </a></td>
                  </tr>
                </table></td>
                <?php  }

if($c == 0) {
				$c = $cols;

		echo "</tr>";
		}}
	else
	{
	 //echo "show";
	}
	}
	
 	//echo "</table>";
	
?>