需要帮助在wordpress网站上缓存json_decode（file_get_contents（'api'））

Question

I'm trying to retrieve data from coinmarketcap's api and store the data to cache file. If the cache file is older than 10 minutes, retrieve new data and store to cache file. I have been able to get everything to work, except for caching the data. The cache file is never created in the plugin directory. Any help would be appreciated. Here is the code :

function Tickers($data){
    foreach($data as $item){
    echo "<a href=/currencies/" .$item->symbol. '/' . $item->name. ">$item->symbol</a>";    
    echo "<br>";
    echo '<span>$' . $item->price_usd . '</span>';
    echo "<br>";
    echo "<br>";
    }
}
function getdata(){
$time = 600; //seconds
$cache_file = 'wp-content/plugins/cryptocurrency_tickers/cache.txt';
if(file_exists($cache_file)){
if(time() - filemtime($cache_file) > $time) {    
// too old , re-fetch
  $data = json_decode(file_get_contents('https://api.coinmarketcap.com/v1/ticker/?limit=20'));
    file_put_contents(cache_file,json_encode($data));
}
    else{
        //data is current
    }
}else {
    // create cache 
    $data = json_decode(file_get_contents('https://api.coinmarketcap.com/v1/ticker/?limit=20'));
    file_put_contents(cache_file, json_encode($data));  
}

$data = json_decode(file_get_contents($cache_file));
Tickers($data);
}

Answer 1

Look at your code again, missing '$' in front of 'cache_file' on file_put_contents

file_put_contents(cache_file,json_encode($data));

should be

file_put_contents($cache_file,json_encode($data));

Also when you get the json data from the API first you decode, then encode, why you didn't save the data directly from the API, it's already json encoded.

Better version of your code:

function Tickers($data){

    foreach($data as $item){
        echo "<a href=/currencies/" .$item->symbol. '/' . $item->name. ">$item->symbol</a>";
        echo "<br>";
        echo '<span>$' . $item->price_usd . '</span>';
        echo "<br>";
        echo "<br>";
    }
}

function getdata(){

    $time       = 600; //seconds
    $cache_file = '/path/to/cache.txt';

    if(file_exists($cache_file)){

        if(time() - filemtime($cache_file) > $time) {
            // too old , re-fetch
            $data = file_get_contents('https://api.coinmarketcap.com/v1/ticker/?limit=20');

            file_put_contents($cache_file, $data);

        } else{
            //data is current
        }
    } else {
        // create cache
        $data = file_get_contents('https://api.coinmarketcap.com/v1/ticker/?limit=20');

        file_put_contents($cache_file, $data);
    }

    $data = json_decode(file_get_contents($cache_file));

    Tickers($data);
}

getdata();

Also make sure the plugin directory is writable by your web server user.