/* PHP FILE - names 'example.php' */

<?php
	$content = file_get_contents('http://site.to.json/');
	echo $content;
?>

/* jQuery making the request */

$.getJSON('example.php', function(data){
	var items = [];

	$.each(data, function(key, val){
                // do stuff with data
		log('key: ' + key + '. value: ' + val);
	});
});

Use PHP to get JSON

1) set the PHP to the URL of the JSON
2) echo a variable with the loaded data
3) use a request via jQuery to get the variable from PHP

JSON with a PHP proxy

php, json

PHP