<?php
// A function to call that will set up & handle the output caching:
// The one optional parameter is to specify how many seconds must pass
// before the page is recreated (defaults to 1 hour)
function cache_page($refresh = 3600) {
// First of all generate the filename for this cache file. Base it upon
// the filename plus GET and POST variables, and use sha1() to hash it
// to a 40 character string so we don't run over filename length limits:
$hash = sha1($_SERVER['PHP_SELF'] . '|G|' . serialize($_GET) .
'|P|' . serialize($_POST));

// Create the actual filename of where to find this. It will be in a
// subdirectory called 'cache' below the location of this library.
$file = dirname(__FILE__) . '/cache/' . $hash;

// Now that we've done all that, see if the last modified time is
// less than the current time plus the refresh time
if ((time() - @filemtime($file)) < $refresh) {
// We are done, just return the file and exit
readfile($file);
exit();
} else {
// Otherwise, we have to actually create the page and save it.
// To do this, first stop the user from aborting at this point so
// it will definitely complete.
ignore_user_abort();

// Now set up a shutdown function, so that we can ensure we actually
// finish up properly when the script exits (for any reason)
register_shutdown_function('_cache_page_exit', $file);

// Now, to finish, we need to start output buffering
ob_start();
}
}

// Create the shutdown function that will be called for us when the script
// exits, allowing us to clean up everything.
function _cache_page_exit($file) {
// We were buffering and are done. First step is to get the contents
// and display it to the user.
$output = ob_get_flush();

// Flush all buffers so the user can get the data while we finish up.
flush();

// Save this data into the cache file, blowing away current contents
// if they existed. Request an exclusive lock for the writing just
// so that two copies of this don't interfere with each other.
file_put_contents($file, $output, LOCK_EX);
}
?>