piccache.php

<?php
define("CACHE_PLACE_PATH", sys_get_temp_dir());
# Also possible:
# define("CACHE_PLACE_PATH", "C:\\your\\Directory");
# define("CACHE_PLACE_PATH", "/var/www/html/directory");
# Remember to set correct privileges allowing PHP access.
function join_paths(...$paths) {
    return preg_replace('~[/\\\\]+~', DIRECTORY_SEPARATOR, implode(DIRECTORY_SEPARATOR, $paths));
};

function get_name($url) {
    $tmp_path = join_paths(CACHE_PLACE_PATH, "piccache");
    if (!file_exists($tmp_path)) mkdir(join_paths($tmp_path), 0777);
    return join_paths($tmp_path, hash('sha256', $url));
}

function get($url) { return file_exists(get_name($url)) ? get_name($url) : null; }

function set($url) {
    $file_name = get_name($url);
    $content = file_get_contents($url);
    file_put_contents($file_name, $content);
    return $file_name;
}

if ($_SERVER['REQUEST_METHOD'] === 'POST') {
    $post = json_decode(file_get_contents('php://input'), true);
    if (! $post || ! array_key_exists("url", $post)) {
        http_response_code(400); exit();
    }
    set($post['url']);
    header('Content-Type: application/json; charset=utf-8');
    echo '{"status": "OK"}' . PHP_EOL;
    exit();
} elseif ($_SERVER['REQUEST_METHOD'] === 'GET') {
    $url = $_GET['url'];
    if (!$url){ http_response_code(400); exit(); }
    $file = get($url);
    header("X-Piccache-Status: ". ($file ? "HIT" : "MISS"));
    if (! $file) $file = set($url);
    $finfo = finfo_open(FILEINFO_MIME);
    header('Content-Type: ' . finfo_file($finfo, $file));
    finfo_close($finfo);
    header('Content-Length: ' . filesize($file));
    $fp = fopen($file, 'rb');
    fpassthru($fp);
    exit();
} else {
    http_response_code(405);
    exit();
}
?>