UTF-8编码怎么去掉BOM头？

<?php

$auto = 1;
checkdir('C:projectweibo');
function checkdir($basedir){
if ($dh = opendir($basedir)) {
  while (($file = readdir($dh)) !== false) {
   if($file{0} == '.')
   {
    continue;
   }
   if ($file != '.' && $file != '..'){
    if (!is_dir($basedir."/".$file)) {
     echo "filename: $basedir/$file ".checkBOM("$basedir/$file")." <br>";
    }else{

     $dirname = $basedir."/".$file;
     checkdir($dirname);
    }
   }
  }
closedir($dh);
}
}
function checkBOM ($filename) {
global $auto;
$contents = file_get_contents($filename);
$charset[1] = substr($contents, 0, 1);
$charset[2] = substr($contents, 1, 1);
$charset[3] = substr($contents, 2, 1);
if (ord($charset[1]) == 239 && ord($charset[2]) == 187 && ord($charset[3]) == 191) {
  if ($auto == 1) {
   $rest = substr($contents, 3);
   rewrite ($filename, $rest);
   return ("<font color=red>BOM found, automatically removed.</font>");
  } else {
   return ("<font color=red>BOM found.</font>");
  }
}
else return ("BOM Not Found.");
}
function rewrite ($filename, $data) {
$filenum = fopen($filename, "w");
flock($filenum, LOCK_EX);
fwrite($filenum, $data);
fclose($filenum);
}
?>

function geturl( $url,$userinfo,$header)
{
 $ch = curl_init();
 $timeout = 1;
 curl_setopt ($ch, CURLOPT_URL, "$url");
 curl_setopt ($ch, CURLOPT_HTTPHEADER, $header);
 curl_setopt ($ch, CURLOPT_REFERER, "http://www.111cn.net/");
 curl_setopt ($ch, CURLOPT_RETURNTRANSFER, 1);
 curl_setopt ($ch, CURLOPT_USERAGENT, "$userinfo");
 curl_setopt ($ch, CURLOPT_CONNECTTIMEOUT, $timeout); 
 $contents = curl_exec($ch);
 curl_close($ch);
 return $contents ;
 
}

set_time_limit(0);//设置超时时间

$str = iconv('gbk','utf-8',$str);

<?php
    header("Content-Type:text/html;charset=utf-8");
?>

Create TABLE `net_city` (
`cityid` smallint(4) NOT NULL auto_increment,
`cityname` varchar(80) NOT NULL default '',
`provinceid` smallint(2) NOT NULL default '0',
`inarea` varchar(5000) NOT NULL default '',
`outarea` varchar(5000) NOT NULL default '',
`tel` varchar(400) NOT NULL default '',
PRIMARY KEY (`cityid`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8;
PHP里的代码：
$conn=mysql_connect("localhost", "用户名", "密码");
mysql_query("set names 'utf8'",$conn);
mysql_select_db(" www.111cn.net 数据名",$conn);
$exec="insert into net_city (cityname,inarea,outarea,tel) values ('".$link_cityname."','".$link_inarea."','".$link_outarea."','".$link_tel."')";

$result=mysql_query($exec,$conn);
if($result){
       echo "1";
     }else{
        echo "0";
     }
mysql_close($conn);

<?php$con = mysql_connect("localhost","peter","abc123");

if (!$con) { die('Could not connect: ' . mysql_error()); }

mysql_select_db("my_db", $con);

mysql_query("SET NAMES GBK");  //GBK处为编码设置

$sql="INSERT INTO person (FirstName, LastName, Age)VALUES('$_POST[firstname]','$_POST[lastname]','$_POST[age]')";

if (!mysql_query($sql,$con))

{ die('Error: ' . mysql_error()); }

echo "1 record added";

mysql_close($con)

?>

Accept text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Encoding gzip, deflate
Accept-Language zh-cn,zh;q=0.8,en-us;q=0.5,en;q=0.3
Connection keep-alive
Cookie __utma=225240837.787252530.1317310581.1335406161.1335411401.1537; __utmz=225240837.1326850415.887.3.utmcsr=google|utmccn=(organic)|utmcmd=organic|utmctr=%E4%BB%BB%E4%BD%95%E9%A1%B9%E7%9B%AE%E9%83%BD%E4%B8%8D%E4%BC%9A%E9%82%A3%E4%B9%88%E7%AE%80%E5%8D%95%20site%3Awww.nowamagic.net; PHPSESSID=888mj4425p8s0m7s0frre3ovc7; __utmc=225240837; __utmb=225240837.1.10.1335411401
Host www.111cn.net
User-Agent Mozilla/5.0 (Windows NT 5.1; rv:12.0) Gecko/20100101 Firefox/12.0

curl_setopt($ch, CURLOPT_ENCODING, "gzip");

$data = file_get_contents("compress.zlib://".$url);