PHP缓存不向文本文件写入任何内容

Question

I try to make my PHP cache with this code:

//Make cache files
$cache = 'tweets-cache.txt';
$date = 'tweets-date.txt';

$currentTime = time(); // Current time


 // Get cache time
$datefile = fopen($date, 'r');
$cacheDate = fgets($datefile);
fclose($datefile);


 //check if cache has expired
if (floor(abs(($currentTime-$cacheDate) / 10800)) <= $_GET['expiry'] && $cacheDate) {
$cachefile = fopen($cache, 'r');
$data = fgets($cachefile);
fclose($cachefile);
} else { 

//Make the REST call
$data = (array) $cb->$api($params);

    // update cache file
    $cachefile = fopen($cache, 'wb');  
    fwrite($cachefile, utf8_encode($data));  
    fclose($cachefile); 
    // update date file
    $datefile = fopen($date, 'wb');  
    fwrite($datefile, utf8_encode(time()));  
    fclose($datefile);      
}

//Output result in JSON, getting it ready for jQuery to process
echo json_encode($data);

Now he writes nothing in tweets-cache.txt. i think it is because of he cannot write an array with utf8_encode.

Answer 1

Yes, you are right about utf8_encode() function. Try to write serialized data to the file:

fwrite($cachefile, json_encode($data));

and when you read your data back from the file, do de-serialization:

$data = json_decode(fgets($cachefile));

Also, you can make things simpler if you use functions like file_get/put_contents, so your code:

$cachefile = fopen($cache, 'r');
$data = fgets($cachefile);
fclose($cachefile);

will be:

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

and:

// update cache file
$cachefile = fopen($cache, 'wb');  
fwrite($cachefile, utf8_encode($data));  
fclose($cachefile); 

// update date file
$datefile = fopen($date, 'wb');  
fwrite($datefile, utf8_encode(time()));  
fclose($datefile);    

translates to:

// update cache file
file_put_contents($cache, json_encode($data));

// update date file  
file_put_contents($date, time());

Be aware of the synchronization problems you can face when you are using filesystem in multithreaded/multiprocess environment. Two and more php instances can make attempt to write data to the same file in the same time, and you will get corrupted file.

You can use filesystem locking or special cache software like Memcached, which is much more preferable solution for such cases.

Memcached

PHP Reference: file_put_contents()

PHP Reference: file_get_contents()

PHP Reference: json_encode()