This example code shows you how to use curl to follow redirects and get final url.

<?php
function get_final_url( $url, $timeout = 5 )
{
    $url = str_replace( "&amp;", "&", urldecode(trim($url)) );
 
    $cookie = tempnam ("/tmp", "CURLCOOKIE");
    $ch = curl_init();
    curl_setopt( $ch, CURLOPT_USERAGENT, "Mozilla/5.0 (Windows; U; Windows NT 5.1; rv:1.7.3) Gecko/20041001 Firefox/0.10.1" );
    curl_setopt( $ch, CURLOPT_URL, $url );
    curl_setopt( $ch, CURLOPT_COOKIEJAR, $cookie );
    curl_setopt( $ch, CURLOPT_FOLLOWLOCATION, true );
    curl_setopt( $ch, CURLOPT_ENCODING, "" );
    curl_setopt( $ch, CURLOPT_RETURNTRANSFER, true );
    curl_setopt( $ch, CURLOPT_AUTOREFERER, true );
    curl_setopt( $ch, CURLOPT_CONNECTTIMEOUT, $timeout );
    curl_setopt( $ch, CURLOPT_TIMEOUT, $timeout );
    curl_setopt( $ch, CURLOPT_MAXREDIRS, 10 );
    $content = curl_exec( $ch );
    $response = curl_getinfo( $ch );
    curl_close ( $ch );
 
    if ($response['http_code'] == 301 || $response['http_code'] == 302)
    {
        ini_set("user_agent", "Mozilla/5.0 (Windows; U; Windows NT 5.1; rv:1.7.3) Gecko/20041001 Firefox/0.10.1");
        $headers = get_headers($response['url']);
 
        $location = "";
        foreach( $headers as $value )
        {
            if ( substr( strtolower($value), 0, 9 ) == "location:" )
                return get_final_url( trim( substr( $value, 9, strlen($value) ) ) );
        }
    }
 
    if ( preg_match("/window.location.replace('(.*)')/i", $content, $value) ||
        preg_match("/window.location=["'](.*)["']/i", $content, $value) ||
        preg_match("/location.href=["'](.*)["']/i", $content, $value) ) { 
        return get_final_url ( $value[1] );
    } else {
        return $response['url'];
    }
}
?>