php如何利用header实现跳转

<?php 
//重定向浏览器 
header("Location: https://ipkd.cn"); 
exit;
?>

<?php 
//重定向浏览器 
header("Location: https://ipkd.cn"); 
exit;
?>

function getref()
{
 $url = @$_SERVER['HTTP_REFERER'];
 if( !empty( $url ) )
 {
 if( !strstr($url ,'jb51.net' ) && !strstr($url,'jb51.net'))
 {
 @header("http/1.1 404 not found");
 @header("status: 404 not found");
 include("404.html");//404页面
 exit();
 }
 }
 else
 {
 @header("http/1.1 404 not found");
 @header("status: 404 not found");
 include("404.html");//404页面
 exit();
 }
}

<?php
 $the_host = $_SERVER['HTTP_HOST'];
 $request_uri = isset($_SERVER['REQUEST_URI']) ? $_SERVER['REQUEST_URI'] : '';
 if($the_host !== 'www.jb51.net')
 {
  //echo $_SERVER['HTTP_HOST'].$_SERVER['PHP_SELF'];
  header('HTTP/1.1 301 Moved Permanently');
  header('Location: https://www.jb51.net' . $_SERVER['PHP_SELF'] . $request_uri);
 }
?>