The document introduces caching in PHP, explaining its purpose to minimize database queries, external requests, computation time, and filesystem access. It outlines how to implement caching using a simple script, discusses various caching methods, and provides performance benchmarks of PHP with and without the APC opcode cache. Additionally, it highlights popular frameworks and CMS that utilize caching techniques to improve performance.

1. Caching Basics in PHP
Presented at
The beauty of Web
phpXperts seminar 2010

2. What is Caching?
“A cache is a temporary storage area
where frequently accessed data can be
stored for rapid access.”

3. Why do we need it?
●
To reduce the number or retrieval queries
made to a database
●
To reduce the number of requests made to
external services
●
To reduce the time spent computing data
●
To reduce filesystem access

4. A basic example
●
A Post
● 23 comments
● Sidebar Contents
●
Navigations
● Categories
● Much more...
We have to load -

5. 1. Check if already cached
if(the resource is cached) {
Just display it.
}
// TOP of your script
$cachefile = 'cache/'.basename($_SERVER['SCRIPT_URI']);
// Serve from the cache if exist
if (file_exists($cachefile)) {
include($cachefile);
exit;
}

6. 2. Generate content and cache
else{
Get the resource, Display it and Cache.
}
ob_start(); // start the output buffer
// – Your normal PHP script and HTML content here –
// BOTTOM of your script
// save the contents of output buffer to the file
$fp = fopen($cachefile, 'w');
fwrite($fp, ob_get_contents());
fclose($fp);
ob_end_flush(); // Send the output to the browser

7. 3. Expire the cache
●
Event/Trigger
●
Setting a time
if(new comment || post edited) {
Expire cache for this post
}
$cachetime = 120 * 60; // 2 hours
// Serve from the cache if it is younger than $cachetime
if (file_exists($cachefile)
&& (time() - $cachetime < filemtime($cachefile))) {
include($cachefile);
Exit;
}

8. So, It was simple. right?
Request
Output
Cache
Compute
Miss
Hit
Store
1
2
3
4
Request

9. Your question is ...
My pages always have an ever changing content
and cannot be cached in their entirety

10. Different Caching Approaches
● Full page caching
● Granular page caching
● Content pre­generation
● Opcode caching
● SQL query caching
● Browser caching
● Object/Variable caching

11. Everybody is doing it!
●
Zend Framework
●
CakePHP
●
Kohana
●
Symfony
●
...
●
Drupal (modules)
●
Wordpress (wp­cache)
●
Joomla (modules)
●
PhpBB
●
Magento
●
...
Frameworks CMSs

12. What to cache?
Anything that...
● you don't want to fetch or compute every time your code runs.
● isn't going to change very often
To find them, monitor ­
● Queries
● Page loads
● Web Analytics

13. Where to Cache?
●
Local Database faster than Remote Database *
●
Local Disk faster than Database*
●
RAM faster than Disk*
* Some conditions apply

14. APC
●
APC: Alternative PHP Cache
●
Free, Open Source Opcode Cache
●
Content / Object caching
●
Simple installation
●
Stores to local, shared memory
●
Going to be released as part of PHP6

15. Installation
Basic PECL (http://pecl.php.net)
pecl install apc
Ubuntu/LinuxMint
apt­get install php5­apc
Windows
(http://pecl4win.php.net )
extension=php_apc.dll

16. A Quick Benchmark
PHP Native PHP w/APC
Concurrency Level 10
Time taken for tests 60 seconds
Complete requests 298 914
Total transferred 643,149 bytes 1,962,675 bytes
HTML transferred 516,971 bytes 1,582,035 bytes
Requests per second 4.91 [#/sec] 15.21 [#/sec]
Time per request 2035.405 [ms] 657.623 [ms]
Time per request
(mean, across all concurrent requests)
203.541 [ms] 65.762 [ms]
Transfer rate 10.35 [KB/s] received 31.88 [KB/s] received

17. How? Opcode caching
Scanning
Lexing
Parsing
Compilation

18. Object caching
● apc_add() / apc_store() ­ Cache a variable
● apc_fetch() ­ Fetch a stored variable from the cache
● apc_delete() ­ Removes a stored variable from the
cache

19. Monitor apc.php

20. I am...
http://ajaxray.com | http://www.facebook.com/ajaxray | http://twitter.com/ajaxray
Anis uddin Ahmad
Co­Founder, WNeeds
http://ajaxray.com | anisniit@gmail.com

21. Thank you!
?
APC Developers
● George Schlossnagle
● Daniel Cowgill
● Rasmus Lerdorf
● Gopal Vijayaraghavan
● Edin Kadribasic
● Ilia Alshanetsky
● Marcus Börger
● Sara Golemon