Adds JSONP support to `jquery.i18n.properties`. See http://code.google.com/p/jquery-i18n-properties/#Known_issues for more info.

jquery.i18n.properties.snippet.js

/* ... snip ... */

/** Load and parse .properties files */
function loadAndParseFile(filename, settings) {
  /* If we are making a cross-domain request, switch to JSONP mode. */
  var dataType = 'text';
  if( /^(https?:)?\/\//.test(filename) ) {
    dataType = 'jsonp';
  }

  $.ajax({
        url:        filename,
        async:      false,
        cache:		settings.cache,
        contentType:'text/plain;charset='+ settings.encoding,
        dataType:   dataType,
        success:    function(data, status) {
        		parseData(data, settings.mode);
			}
    });
}

/* ... snip ... */

/* Invoke like this: */
(function($) {
  $(function() {
    $.i18n.properties({
      path:     'http://www.example.com/path/to/serverside-i18n.php?file=',
      /* ... */
    });
  })
})(jQuery);

serverside-i18n.php

<?php
foreach( array('file', 'callback') as $key )
{
  if( empty($_GET[$key]) )
  {
    header('HTTP/1.0 400 Bad Request');
    exit;
  }
}

$file = $_GET['file'];
$func = $_GET['callback'];

# @todo Verify that file has the correct naming format.
$path = sprintf('%s/%s', __DIR__, basename($file));

if( is_file($path) )
{
  header('Content-type: application/javascript');

  printf(
    '%s(%s);'
      , $func
      , json_encode(file_get_contents($path))
  );
}
else
{
  header('HTTP/1.0 404 Not Found');
}