jsonp-callback-example.php

<?php
header('Content-Type: application/json');

$callback = isset($_GET['callback']) ? $_GET['callback'] : false;

$output = array(
	'some' => 'data'
);

$output = json_encode($output);

if ($callback) {
	echo sprintf('%s(%s)', $callback, $output);
} else {
	echo $output;
}