Does file_get_contents use a cache?

Question

I have a function that generates a table with contents from the DB. Some cells have custom HTML which I'm reading in with file_get_contents through a templating system.

The small content is the same but this action is performed maybe 15 times (I have a limit of 15 table rows per page). So does file_get_contents cache if it sees that the content is the same?

file_get_contents is basically just a shortcut for fopen, fread, fclose etc - so I imagine opening a file pointer and freading it isn't cached. — Jimbo, Aug 07 '13 at 07:42
Is there a file reading function in PHP where I can choose `$cache = true`? — silkfire, Aug 07 '13 at 07:43
http://stackoverflow.com/questions/16888087/php-file-get-contents-multiple-times-for-the-same-file — Marty, Aug 07 '13 at 07:48
readfile() function seems to support caching - http://php.net/manual/en/function.readfile.php — Vladimir Hraban, Aug 07 '13 at 07:48
http://stackoverflow.com/questions/11708332/does-file-get-contents-use-a-cache please refer it also. That will be helpful to you. — Pratik, Aug 07 '13 at 07:48
@VladimirHraban readfile can't store contents in a $variable — silkfire, Aug 07 '13 at 07:49
@silkfire It will if you use output buffer :) ob_start(), ob_get_contents(), ob_end_clean(); — Vladimir Hraban, Aug 07 '13 at 07:51

Raptor · Answer 1 · 2015-01-28T02:19:06.350

9

file_get_contents() does not have caching mechanism. However, you can use write your own caching mechanism.

Here is a draft :

$cache_file = 'content.cache';
if(file_exists($cache_file)) {
  if(time() - filemtime($cache_file) > 86400) {
     // too old , re-fetch
     $cache = file_get_contents('YOUR FILE SOURCE');
     file_put_contents($cache_file, $cache);
  } else {
     // cache is still fresh
  }
} else {
  // no cache, create one
  $cache = file_get_contents('YOUR FILE SOURCE');
  file_put_contents($cache_file, $cache);
}

UPDATE the previous if case is incorrect, now rectified by comparing to current time. Thanks @Arrakeen.

edited Jan 28 '15 at 02:19

answered Aug 07 '13 at 07:44

Raptor

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3

PHP has a native support of caching called APC - http://php.net/manual/en/book.apc.php – Vladimir Hraban Aug 07 '13 at 07:45
20

So... you're caching the contents of a file in a file...?!?! – deceze Aug 07 '13 at 07:49
3

This actually will make it slower. – Gerry Aug 07 '13 at 07:50
Here's an interesting article about `file_get_contents()` and `APC`: https://blogs.oracle.com/basant/entry/caching_file_get_contents_output – Raptor Aug 07 '13 at 07:50
4

@Gerry not really, if the file source is from network, it will make it faster – Raptor Aug 07 '13 at 07:51
@ShivanRaptor I am afraid the link to the patch provided in the article is broken :-( Is there an alternative? – Vladimir Hraban Aug 07 '13 at 07:54
1

This would work if the `filemtime()` function would be properly compared with the current time, in fact in this example `if(filemtime($cache_file) > 86400)` will always be `true`. – Mooncake Jan 26 '15 at 10:46

score 4 · Answer 2 · answered Dec 25 '13 at 00:30

Like @deceze says, generally the answer is no. However operating system level caches may cache recently used files to make for quicker access, but I wouldn't count on those being available. If you'd like to cache a file that is being read multiple times per request, consider using a static variable to act as a cache inside a wrapper function.

function my_file_read($filename) {
  static $file_contents = array();
  if (!isset($file_contents[$filename])) {
    $file_contents[$filename] = file_get_contents($filename);
  }
  return $file_contents[$filename];
}

Calling my_file_read($filename) multiple times will only read the file from disk a single time, subsequent calls will read the value from the static variable within the function. Note that you shouldn't count on this approach for large files or ones used only once per page, since the memory used by the static variable will persist until the end of the request. Keeping the contents of files unnecessarily in static variables is a good way to make your script a memory hog.

score 3 · Answer 3 · answered Dec 07 '18 at 01:43

The correct answer is yes. All the PHP file system functions do their own caching, and you can use the "realpath_cache_size = 0" directive in PHP.ini to disable the caching if you like. The default caching timeout is 120 seconds. This is separate from the caching typically done by browsers for all GET requests (the majority of Web accesses) unless the HTTP headers override it. Caching is not a good idea during development work, since your code may read in old data from a file whose contents you have changed.

`realpath_cache_size` only caches real pathes of the files, not results of file reading operations. More detailed at https://www.php.net/manual/en/function.realpath-cache-size.php#101840 — xmike, May 14 '21 at 11:00

Does file_get_contents use a cache?

3 Answers3

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