<?php
class timeKeeper{
    public static $json_filename = "abc.json";
    public static $json_api_url = "https://example.com/api/?v=1.333";
    public static function judge(){
        $server_timestamp = time();
        $server_time = date('Y/m/d H',$server_timestamp);
        $json_timestamp = filemtime(self::$json_filename);
        $json_time = date('Y/m/d H',$json_timestamp);
        return $server_time === $json_time ? true : false;
    }
    public static function api_run($opts=null){
        if(is_null($opts))return false;
        $context = stream_context_create($opts);
        $json = file_get_contents(self::$json_api_url, false, $context);
        $fp = fopen(self::$json_filename, "w");
        fwrite($fp,$json);
        fclose($fp);
        return self::json_load();
    }
    public static function json_load(){
        $json = file_get_contents(self::$json_filename);
        return json_decode($json, true);
    }
    public static function check(){
        if(file_exists(self::$json_filename)){
            return self::judge();
        }
        return false;
    }
}
///使用例
if(timeKeeper::check()){
   $json = timeKeeper::json_load();
}else{
    $opts = array(
        "http"=>array(
        "method" => "POST",
        "header" => "User-Agent: php"
        )
    );
    $json = timeKeeper::api_run($opts);
}