Caching basics in PHP

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

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

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

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

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; }

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

3. Expire the cache ● Event/Trigger if(new comment || post edited) { Expire cache for this post } ● Setting a time $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; }

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

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

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

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

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

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

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

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

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 203.541 [ms] 65.762 [ms] (mean, across all concurrent requests) Transfer rate 10.35 [KB/s] received 31.88 [KB/s] received

How? Opcode caching Scanning Lexing Parsing Compilation

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

Monitor apc.php

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

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

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Caching basics in PHP

by Anis Ahmad on Nov 06, 2010

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Caching basics in PHP — Presentation Transcript