json_encode. Workaround for PHP < 5.1.6

callback.php

/**
 * Workaround for PHP < 5.1.6
 */
if (!function_exists('json_encode')) {
	function json_encode($data) {
		switch ($type = gettype($data)) {
			case 'NULL':
				return 'null';
			case 'boolean':
				return ($data ? 'true' : 'false');
			case 'integer':
			case 'double':
			case 'float':
				return $data;
			case 'string':
				return '"' . addslashes($data) . '"';
			case 'object':
				$data = get_object_vars($data);
			case 'array':
				$output_index_count = 0;
				$output_indexed = array();
				$output_associative = array();
				foreach ($data as $key => $value) {
					$output_indexed[] = json_encode($value);
					$output_associative[] = json_encode($key) . ':' . json_encode($value);
					if ($output_index_count !== NULL && $output_index_count++ !== $key) {
						$output_index_count = NULL;
					}
				}
				if ($output_index_count !== NULL) {
					return '[' . implode(',', $output_indexed) . ']';
				} else {
					return '{' . implode(',', $output_associative) . '}';
				}
			default:
				return ''; // Not supported
		}
	}
}