How do I cache a web page in PHP?

how do I cache a web page in php so that if a page has not been updated viewers should get a cached copy?

Thanks for your help. PS: I am beginner in php.

Answer

You can actually save the output of the page before you end the script, then load the cache at the start of the script.

example code:

<?php

$cachefile = 'cache/'.basename($_SERVER['PHP_SELF']).'.cache'; // e.g. cache/index.php.cache
$cachetime = 3600; // time to cache in seconds

if (file_exists($cachefile) && time() - $cachetime <= filemtime($cachefile)) {
  $c = @file_get_contents($cachefile);
  echo $c;
  exit;
} else {
  unlink($cachefile);
}

ob_start();

// all the coding goes here

$c = ob_get_contents();
file_put_contents($cachefile, $c);

?>

If you have a lot of pages needing this caching you can do this:

in cachestart.php:

<?php
$cachefile = 'cache/' . basename($_SERVER['PHP_SELF']) . '.cache'; // e.g. cache/index.php.cache
$cachetime = 3600; // time to cache in seconds

if (file_exists($cachefile) && time() - $cachetime <= filemtime($cachefile)) {
  $c = @file_get_contents($cachefile);
  echo $c;
  exit;
} else {
  unlink($cachefile);
}

ob_start();
?>

in cacheend.php:

<?php

$c = ob_get_contents();
file_put_contents($cachefile, $c);

?>

Then just simply add

include('cachestart.php');

at the start of your scripts. and add

include('cacheend.php');

at the end of your scripts. Remember to have a folder named cache and allow PHP to access it.

Also do remember that if you’re doing a full page cache, your page should not have SESSION specific display (e.g. display members’ bar or what) because they will be cached as well. Look at a framework for specific-caching (variable or part of the page).