How to redirect your complete old domain url to new domain in PHP

<?php  
$pageURL = (@$_SERVER["HTTPS"] == "on") ? "https://" : "http://";
if ($_SERVER["SERVER_PORT"] != "80")
{
 $pageURL .= $_SERVER["SERVER_NAME"].":".$_SERVER["SERVER_PORT"].$_SERVER["REQUEST_URI"];
} 
else 
{
 $pageURL .= $_SERVER["SERVER_NAME"].$_SERVER["REQUEST_URI"];
}

$goto =  str_replace("olddomain.com", "newdomain.com",strtolower($pageURL));

header ("Location: $goto");  
?>