获取链接最终跳转地址的PHP代码

<?php
$url = $_GET['url'];
$url = str_replace(' ','%20',$url);
$url = str_replace(':','%3A',$url);
$url = str_replace('%3A//','://',$url);
function getrealurl($url){
    $header = get_headers($url,1);
    if (strpos($header[0],'301') || strpos($header[0],'302')) {
        if(is_array($header['Location'])) {
            return $header['Location'][count($header['Location'])-1];
        }else{
            return $header['Location'];
        }
    }else {
        return $url;
    }
}
echo getrealurl($url);

在传递get参数时，&写为%26