file cache & output buffering או איך להחזיר את כח השרת האבוד

<?php ob_start(); echo 'everything will be buffered first';

<?php
function callback($buffer) { return $buffer; }
ob_start('callback');
echo 'everything will be buffered first';

<?php
error_reporting(E_ALL);


$_cache['time_to_cache'] = 1800;
$_cache['directory'] = 'cache';

function save_cache($data)
{
  global $_cache;
 
  chdir(dirname(__FILE__));
 
  // create the cache file
  if(!touch($_cache['url'])) return 'failed to create cache file. check directory permissions';

  // write the data to the cache file
  file_put_contents($_cache['url'], $data);
   
  // the return value is being echoed
  return  $data;
}

function cache_by_query_string( )
{
  global $_cache;
 
  // get url file name (/directory/script.php?x=1&y=2)
  $url = $_SERVER["PHP_SELF"] . '?' . $_SERVER["QUERY_STRING"];
 
  // encode the url (%2Fdirectory%2Fscript.php%3Fx%3D1%26y%3D2)
  $url = urlencode($url);
 
  // find out the name of the cache file
  // cache/%2Fdirectory%2Fscript.php%3Fx%3D1%26y%3D2.cache
  $cache_file_name = $_cache['directory'] .'/'. $url . '.cache';
 
  clearstatcache();
  if( file_exists($cache_file_name) )
  {
    // last file's modification time
    $last_cache_time = filectime($cache_file_name);
   
    // if the file was modified in the last X seconds -> it's good
    // otherwise, it's too old
    if( $last_cache_time + $_cache['time_to_cache'] > time() )
    {
      ob_clean();
      readfile($cache_file_name);
      exit();
    }
  }
 
  ob_start('save_cache');
  $_cache['url'] = $cache_file_name;
   
}

// start the caching procedure
cache_by_query_string();

/********** ALL YOUR CODE GOES BELOW ************/

echo 'hey, hi, heya';
if( isset($_GET['id']) ) echo 'this page cached with id ', $_GET['id'];