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PHP remote file/URL cache
A simple cache for remote files/URLs
2011 Carlo Alberto Ferraris <>
The cache function allows you to get the contents of a remote URL at
most once every N seconds. It also supports the If-Modified-Since HTTP
header to avoid fetching the resource again if it hasn't changed.
The url_get_contents is a convenience wrapper around file_get_contents
and cache.
To make sure of requesting a certain $url at most every $seconds:
$url_or_filename = cache($url, $seconds);
so, instead of e.g.
you can write, to request the URL at most once per minute (60 seconds):
file_get_contents(cache("", 60));
or, alternatively,
url_get_contents("", 60);
The value returned by cache can be either a full path to a local file
(cached) or the requested URL (in case something failed).
The value returned by url_get_contents is the one returned by a call
to file_get_contents.
define('CACHE_PREFIX', 'cache_');
define('CACHE_DIR', sys_get_temp_dir());
function cache($url, $min_expiration) {
$min_expiration = max( intval( $min_expiration ), 1 );
$cache_key = sha256($url) or return $url;
$cache_file_name = CACHE_PREFIX . $cache_key;
$cache_file_fullpath = CACHE_DIR . '/' . $cache_file;
$cache_file_mtime = @filemtime($cache_file_fullpath);
if ($cache_file_mtime && $cache_file_mtime >= time() - $min_expiration) {
// we have a cached version less than $min_expiration seconds old - return it
return $cache_file_fullpath;
$url_or_file = $cache_file_mtime ? $cache_file_fullpath : $url;
// try to acquire a lock for the url: if it fails either return the stale cached
// version (if available), the original url otherwise
$lockn = $cache_file_fullpath . '.lock';
$lockp = @fopen($lockn, 'w+') or return $url_or_file;
@flock($lockp, LOCK_EX|LOCK_NB) or return $url_or_file;
// we have our lock, now fetch the url and save it in a temporary file
$fn = @tempnam(CACHE_DIR) or return $url_or_file;
$fp = @fopen($fn, 'w+b') or return $url_or_file;
$c = @curl_init() or return $url_or_file;
@curl_setopt($c, CURLOPT_URL, $url) or return $url_or_file;
@curl_setopt($c, CURLOPT_FILE, $fp) or return $url_or_file;
@curl_setopt($c, CURLOPT_FOLLOWLOCATION, true) or return $url_or_file;
@curl_setopt($c, CURLOPT_AUTOREFERER, true) or return $url_or_file;
@curl_setopt($c, CURLOPT_MAXREDIRS, 5) or return $url_or_file;
if ($cache_file_mtime)
@curl_setopt($c, CURLOPT_TIMEVALUE, $cache_file_mtime);
@curl_exec($c) or return $url_or_file;
$cs = intval(@curl_getinfo($c, CURLINFO_HTTP_CODE));
// we finished fetching the url: if it ended succesfully, delete the old cached
// version and replace it with the new one
if ($cs >= 200 && $cs < 300) {
@unlink($cache_file_fullpath) or return $url;
@link($fn, $cache_file_fullpath) or return $url;
// release the lock, close and remove the temporary files
return $cache_file_fullpath;
function url_get_contents($url, $min_expiration=60) {
return file_get_contents( cache( $url, $min_expiration ) );

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@diachedelic diachedelic commented Feb 14, 2019

This looks like just what I need, but my PHP interpreter doesn't like the or return statements:

$ php -v
PHP 7.1.23 (cli) (built: Nov  7 2018 18:20:35) ( NTS )
Copyright (c) 1997-2018 The PHP Group
Zend Engine v3.1.0, Copyright (c) 1998-2018 Zend Technologies
<b>Parse error</b>:  syntax error, unexpected 'return' (T_RETURN) in <b>....../</b> on line <b>41</b><br />

Relevant line: $cache_key = sha256($url) or return $url;.

Seems like it's not legal in PHP!?

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