HTTP Cross-Domain Communication: An AJAX Dilemma

XMLHttpRequest, the backbone of AJAX technology, enforces a cross-domain policy that hinders direct communication with external servers. Attempting to retrieve data from a different domain using an AJAX request results in an accessibility error.

To overcome this restriction, JSONP was introduced. However, it often introduces syntactical errors due to the mismatch between the expected JSON format and the received data.

The Only Viable Solution: A Server-Side Proxy

The most practical solution is to employ a server-side language as a proxy. This technique allows you to access cross-domain data indirectly through an intermediate script running on your server.

Implementation Using jQuery and PHP

To implement a cross-domain data retrieval using jQuery and PHP:

jQuery Portion:

$.ajax({
    url: 'proxy.php',
    type: 'POST',
    data: {
        address: 'http://www.google.com'
    },
    success: function(response) {
        // response now contains full HTML of google.com
    }
});

PHP Proxy (proxy.php):

echo file_get_contents($_POST['address']);

By utilizing this approach, you can effectively access and display data from foreign domains while adhering to the AJAX cross-domain policy. Be mindful of any restrictions or potential issues with the scraped data.