Simple cache proxy to throttle queries to APIs, for example to darksky.net

cache-proxy.php

<?php
/* Cache proxy for darksky.net API requests */
define('API_KEY', '***********************');
define('TIMEOUT', 10 * 60); // In seconds (10 minutes)

// Coordinates MUST be the first element in URL as https://api.server.io/v1/weather/[LAT,LON]
$params = explode('/', trim($_SERVER['PATH_INFO'], '/'));
$coords = filter_var(array_shift($params), FILTER_SANITIZE_STRING);

// Validate coordinates
if (empty($coords)) sendResponse(400, ["code" => 400, "message" => "Coordinates are required"]);
$latlon = explode(',', $coords);
if (count($latlon) != 2) sendResponse(400, ["code" => 400, "message" => "Invalid coordinates"]);

// Retrieve information
$url = 'https://api.darksky.net/forecast/'.API_KEY.'/'.$coords.'?exclude=[minutely,hourly]&units=si&lang=ca';
$file = 'cache/'.md5($url).'.json';
if (!file_exists($file) || (time() - filemtime($file) > TIMEOUT)) {
	// Return from API & update cache
	$response = file_get_contents($url);
	if (!file_exists('cache')) mkdir('cache', 0777);
	file_put_contents($file, $response);
	sendResponse(200, $response);
} else sendResponse(200, file_get_contents($file)); // Return from cache

// Send HTTP response
function sendResponse($code, $response) {
	header("HTTP/1.0 ".$code);
	header('Content-type: application/json');
	echo is_array($response)
		? json_encode($response, JSON_UNESCAPED_SLASHES | JSON_NUMERIC_CHECK)
		: $response;
	exit();
}

?>