PHP Cache Dynamic Pages To Speed Up Load Times

If your website receives a good amount of traffic every day and your web pages are loading slow, you might want to consider implementing some sort of caching mechanism on your website to speed up page loading time. Because as we all know that each client-server request consists of many queries, loops, calculations, database queries etc. these all add up to processing time, which eventually increases page loading time. The simplest way to avoid all these is to create cache files and store them in a separate directory, which can later be served as fast loading static pages instead of dynamically generated pages.

PHP Caching

There are several other PHP cache engines such as APC, Xcache or OPcache to boost your application performance, but they all work quite differently if you are curious; you can always find plenty of articles and tutorials written about them on the web. But here you’ll learn the simplest way of caching PHP pages, and that is using PHP’s core output Buffer and Filesystem, combining these two functions we can have a magnificent caching system..

PHP Output buffer :— It interestingly improves performance and decreases the amount of time it takes to download, because the output is not being sent to browser in pieces but the whole HTML page as one variable. The method is insanely simple take a look at the code below :

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<?php
ob_start(); // start the output buffer

/* the content */
ob_get_contents();  gets the contents of the output buffer
ob_end_flush(); // Send the output and turn off output buffering
?>

First line ob_start() turns the output buffering on, which means anything after this will be stored in the buffer and to retrive the contents of the output buffer we simply call ob_get_contents(). The ob_end_flush() at the end of the code turns buffering off.

PHP Filesystem :— is a also a part of the PHP core, which allow us to read and write the file system.

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$fp = fopen('/path/to/file.txt', 'w');  //open file for writing
fwrite($fp, 'I want to write this'); //write
fclose($fp); //Close file pointer

As you can see the first line of the code fopen() opens the file for writing, the mode ‘w’ places the file pointer at the beginning of the file and if file does not exist, it attempts to create one. Second line fwrite() writes the string to the opened file, and finally fclose() closes the successfully opened file at the beginning of the code.

Implementing PHP caching

Now you should be pretty clear about PHP output buffer and filesystem, we will use both methods to create our simple PHP caching system. Please have a look at the picture below, the flowchart gives you the basic idea of our cache system.
PHP cache system in Action
The cycle starts when a user requests the content, the script simply checks and outputs the cache copy of requested page, if it doesn’t a new copy is created and sent to the browser.

Below is the full example of PHP caching system, you can examine, copy it into your PHP project and play with code, it should work as expected. You can modify the cache expire time, cache file extension, ignored pages etc. to suit your needs.

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<?php
//settings
$cache_ext  = '.html'; //file extension
$cache_time     = 3600;  //Cache file expires afere these seconds (1 hour = 3600 sec)
$cache_folder   = 'cache/'; //folder to store Cache files
$ignore_pages   = array('', '');

$dynamic_url    = 'http://'.$_SERVER['HTTP_HOST'] . $_SERVER['REQUEST_URI'] . $_SERVER['QUERY_STRING']; // requested dynamic page (full url)
$cache_file     = $cache_folder.md5($dynamic_url).$cache_ext; // construct a cache file
$ignore = (in_array($dynamic_url,$ignore_pages))?true:false; //check if url is in ignore list

if (!$ignore && file_exists($cache_file) && time() - $cache_time < filemtime($cache_file)) { //check Cache exist and it's not expired.
    ob_start('ob_gzhandler'); //Turn on output buffering, "ob_gzhandler" for the compressed page with gzip.
    readfile($cache_file); //read Cache file
    echo '<!-- cached page - '.date('l jS \of F Y h:i:s A', filemtime($cache_file)).', Page : '.$dynamic_url.' -->';
    ob_end_flush(); //Flush and turn off output buffering
    exit(); //no need to proceed further, exit the flow.
}
//Turn on output buffering with gzip compression.
ob_start('ob_gzhandler');
######## Your Website Content Starts Below #########
?>
<!DOCTYPE html>
<html>
    <head>
        <title>Page to Cache</title>
    </head>
        <body>
            Lorem ipsum dolor sit amet, consectetur adipiscing elit. Integer ut tellus libero.
        </body>
</html>
<?php
######## Your Website Content Ends here #########

if (!is_dir($cache_folder)) { //create a new folder if we need to
    mkdir($cache_folder);
}
if(!$ignore){
    $fp = fopen($cache_file, 'w');  //open file for writing
    fwrite($fp, ob_get_contents()); //write contents of the output buffer in Cache file
    fclose($fp); //Close file pointer
}
ob_end_flush(); //Flush and turn off output buffering

?>

Here’s quick points to help you understand the code:

  1. Get current page URL, convert it to MD5 hash for file naming.
  2. Check whether URL is in ignore list.
  3. Check for unexpired cache file and output with “ob_gzhandler” gzip output buffer, or create new.

Conclusion

I hope this script helps you create your own simple caching system, but you must avoid caching certain types of pages such as members area (after users log in), search pages or constantly updating pages, your users will experience undesirable outcomes. And remember just caching pages isn’t enough, consider combining and compressing JavaScripts, CSS to boost performance, even more, use various tricks and tips, dig deeper, use free tools like Google’s pageSpeed, Chrome DevTools to analyze performance of your website, good luck.

  1. Excellent code save lot’s of time. Great keep posting.

     Reply
  2. Hi, this is great but how can i set the $cache_time for like 7 days instead of seconds?

     Reply
  3. Carlos Devia Rojas

    This cache script works perfect wrapping the index.php of a prestashop installation:

    Combining some rules in https://github.com/CleverCloud/varnish-examples/blob/master/prestashop.vcl works perfect .

    You only have to add the URL for shopping cart and avoid any cache when a POST request is made with:

    if ($_SERVER[‘REQUEST_METHOD’] != ‘GET’) {
    $ignore = true;
    }

    Ask us any information if you want to implement it in a prestashop system: https://www.imaginacolombia.com

    Regards

     Reply
  4. Very helpful information and add insight .. Thanks

     Reply
  5. Thank you, thank you, thank you.

     Reply
  6. Hi Steve,

    I want to use cache system in my list pages. But I have some dynmic fields like a vote buttons or ‘an hour ago’ etc.

    What should I do? I need logical behind more than codes. Thank u.

     Reply
  7. Hey! thanks for the code. It works great!

     Reply
  8. Thanks a lot for this great cache script!
    I visit your site often while there is a lot of interesting info for me.
    After putting this script into a page and testing it, the loading time decreased from about 400ms to 60ms!!!!!

     Reply
  9. Hey, this worked great, thank you so much for the code!!!

     Reply
    • Also, how do you flush the cache when you’ve updated the page (let’s say you’re doing testing) and want to see the updated page? Is there an easy part in the code to comment out? Thanks!

  10. thanks for this tutorial, very helpfull

     Reply
  11. How about image ? Is including too on cache file? My html content using a lot of images that make loading take long time.

     Reply
  12. hmmm :D thanks, its really help

     Reply
  13. if i a have a dynamic page which fetches 5 records from database.
    tomorrow someone adds the sixth record
    and i again hit the same url will it show me 5 records or 6 records ?
    what do you mean by this : if the Web developer manually edits the file

     Reply
    • All that is required of you is to set an appropriate cache time. In my case, I will be modifying the code, I can use an unlimited cache time, since all my content is moderated, and I shall be coding a cache purge upon authorizing a change to the site. You may consider this technique for yourself, if it is a special interest to your situation, on top of a cache time, as well.

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