使用到期日期在服务器上缓存 JSON？

Question

This is some working code that I wrote to call a JSON file and cache it on my servers.

I'm calling the cached file. If the file exists I use json_decode on it. If the file doesn't exist I then call the JSON and decode that. Then after calling the JSON url, I write the contents to the cached file url.

$cache = @file_get_contents('cache/'.$filename.'.txt');

 //check to see if file exists:
if (strlen($cache)<1) {

    // file is empty
    echo '<notcached />';
    $JSON1= @file_get_contents($url);

    $JSON_Data1 = json_decode($JSON1);

    $myfile = fopen('cache/'.$filename.'.txt', "w");
    $put = file_put_contents('cache/'.$filename.'.txt', ($JSON1));

} else {

    //if file doesn't exist:
    $JSON_Data1 = json_decode($cache);
    echo '<cached />';
}

Instead of only using if (strlen($cache)<1) { , is there a way that I can check the age of the $filename.txt and if it's older than 30 days grab the JSON url in the else statement?

Answer 1

You can use something like

$file = 'cache/'.$filename.'.txt';
$modify = filemtime($file);
//check to see if file exists:
if ($modify == false || $modify < strtotime('now -30 day')) {
    // file is empty, or too old
    echo '<notcached />';
} else {
    // Good to use file
    echo '<cached />';
}

filemtime() returns the last modified time of the file, the if statement checks that the file exists ( filemtime returns false if it fails) or the file was last modified more than 30 days ago.

OR... to check if the file exists or too old (without warnings)

$file = 'cache/'.$filename.'.txt';
if (file_exists($file) == false || filemtime($file) < strtotime('now -30 day')) {
    // file is empty, or too old
    echo '<notcached />';
} else {
    // Good to use file
    echo '<cached />';
}

Answer 2

I've used a simple file cache class in my previous projects, I think that should help you. I think it's easy to understand, the cache time is in seconds and the setFilename function cleans the filename in case it contains invalid characters.

<?php

class SimpleFileCache
{
    var $cache_path = 'cache/';
    var $cache_time = 3600;
    var $cache_file;

    function __construct($name)
    {
        $this->setFilename($name);
    }

    function getFilename()
    {
        return $this->cache_file;
    }

    function setFilename($name)
    {
        $this->cache_file = $this->cache_path . preg_replace('/[^0-9a-z\.\_\-]/', '', strtolower($name));
    }

    function isCached()
    {
        return (file_exists($this->cache_file) && (filemtime($this->cache_file) + $this->cache_time >= time()));
    }

    function getData()
    {
        return file_get_contents($this->cache_file);
    }

    function setData($data)
    {
        if (!empty($data)) {
            return file_put_contents($this->cache_file, $data) > 0;
        }
        return false;
    }
}

It can be used like this.

<?php

require_once 'SimpleFileCache.php';

$cache = new SimpleFileCache('cache.json');
if ($cache->isCached()) {
    $json = $cache->getData();
} else {
    $json = json_encode($someData); // set your cache data
    $cache->setData($json);
}

header('Content-type: application/json');
echo $json;