Adds basic caching functionality to Pico

PicoCaching.php

<?php

/* 
Creates a 'cache.php' file in the content directory, containing all pages. 
The file is being kept for a day, page changes will be ignored as long the cache file exists. 
You can simply delete the cache file in order to refresh the pages and contents
*/

class PicoCaching extends AbstractPicoPlugin {

    const API_VERSION = 2;

    private $cachingFile;
    private $cache;
    private $createCache = true;

    public function onConfigLoaded(&$config) {
        $this->cachingFile = $config['content_dir'].'cache.php';
    }
    
    public function onPagesLoading() {
        if (!file_exists($this->cachingFile)) {
            return;
        }

        $cache = unserialize(file_get_contents($this->cachingFile));

        if ((time() - intval($cache['date_created'])) > 86400) {
            unlink($this->cachingFile);
            return;
        }

        $this->createCache = false;
        $this->cache = $cache['cache'];
    }

    public function onSinglePageLoading($id, &$skipFile) {
        if ($this->createCache == false) {
            $skipFile = true;
        }
    }

    public function onPagesLoaded(&$pages) {
        if ($this->createCache) {
            $cache = array('date_created' => time(), 'cache' => $pages);
            file_put_contents($this->cachingFile, serialize($cache));
        } else {
            $pages = $this->cache;
        }
    }
}