Same Origin Policy, Javascript/jQuery AJAX and retrieving an RSS XML feed

I came across a problem using jQuery to retrieve an RSS feed located on an external domain. It was working in Safari but other browsers would error because of Same Origin Policy restrictions (which are also documented about the $.ajax() func开发者_运维知识库tion).

Wanna know how I fixed it?

There are three ways to get around the Same-Origin Policy:

1. Proxy -- as Strawberry Sheurbert did, perfectly effective but a waste of bandwidth and computing power
2. JSONP -- loading the data through the script tag. Needs cooperation from source website and basically hackish and clumsy.
3. CORS -- the "right" way, elegant and nuanced, but needs a lot of cooperation from source website and doesn't work with older browsers.

You pays your money and you takes your chance.

I made a simple PHP script like so:

<?php

/*
    fetch.php fixes this issue: http://en.wikipedia.org/wiki/Same_origin_policy

    Read more:
        *   http://api.jquery.com/jQuery.ajax/
        *   http://stackoverflow.com/questions/3595515/xmlhttprequest-error-origin-null-is-not-allowed-by-access-control-allow-origin
        *   http://stackoverflow.com/questions/1653308/access-control-allow-origin-multiple-origin-domains
*/

// Requires URL
if ( !isset($_REQUEST['url']) || empty($_REQUEST['url']) ) exit( 'No url specified' );

// Set content-type
$type = 'application/rss+xml; charset=utf-8;';
if ( isset($_REQUEST['type']) && !empty($_REQUEST['type']) ) {
    $type = urldecode($_REQUEST['type']);
}

// Adapted from http://www.howtogeek.com/howto/programming/php-get-the-contents-of-a-web-page-rss-feed-or-xml-file-into-a-string-variable/
function get_url_contents( $url ){
    if ( function_exists('curl_init') ) {
        $crl = curl_init();
        $timeout = 5;
        curl_setopt ($crl, CURLOPT_URL, $url);
        curl_setopt ($crl, CURLOPT_RETURNTRANSFER, 1);
        curl_setopt ($crl, CURLOPT_CONNECTTIMEOUT, $timeout);
        $ret = curl_exec($crl);
        curl_close($crl);
        return $ret;
    } else {
        return file_get_contents( $url );
    }
    return 'Could not retrieve url';
}

// Output content from url
header( 'Content-type: ' . $type );
echo get_url_contents( urldecode($_REQUEST['url']) );


?>

It's pretty rubbish looking, but it works well enough for the moment. I hope it helps.