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For 2023 (and 2024 ...) - we are now fully retired from IT training.
We have made many, many friends over 25 years of teaching about Python, Tcl, Perl, PHP, Lua, Java, C and C++ - and MySQL, Linux and Solaris/SunOS too. Our training notes are now very much out of date, but due to upward compatability most of our examples remain operational and even relevant ad you are welcome to make us if them "as seen" and at your own risk.

Lisa and I (Graham) now live in what was our training centre in Melksham - happy to meet with former delegates here - but do check ahead before coming round. We are far from inactive - rather, enjoying the times that we are retired but still healthy enough in mind and body to be active!

I am also active in many other area and still look after a lot of web sites - you can find an index ((here))
Caching results in an object for efficiency - avoiding re-calculation

Do you like to do the same thing time and time and time again? Probably not, as it's boring and inefficient. Computers don't get bored, but they can be inefficient if not programed well ... and because they don't get bored, they don't complain if they're inefficient.

Imagine you have a class of objects on which you need to perform a complex calculation.

Scenario 1 ... you create 100 objects but only need the calculation results from 10 of them

Scenario 2 ... you create 5 objects and need the results from each of them 10 times over.

If you do the calculation as you enter data into the objects, you'll do 100 calculations in the first scenario and 5 in the second - total 105

If you do the calculatio as you get the results out, you'll do 10 calculations in the first scenario and 50 in the second - total 60

If you calculate the results just in time and store them in the object when calculates (cache the answer) you only need to make 10 calculations for the first scenario and 5 for the second - total 15.

Sample program - [here].
(written 2016-01-20)

 
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
H108 - Objects in PHP
  [67] Object Oriented Programming in PHP - (2004-09-29)
  [124] PHP v Java - (2004-11-20)
  [205] PHP5 lets you say no - (2005-02-07)
  [343] Should I use structured or object oriented? - (2005-06-10)
  [421] Don't repeat code - use loops or functions - (2005-08-21)
  [485] North, Norther and Northest - PHP 5 Objects - (2005-11-04)
  [656] Think about your design even if you don't use full UML - (2006-03-24)
  [720] Planning a hotel refurb - an example of a Gant chart in PHP - (2006-05-14)
  [836] Build on what you already have with OO - (2006-08-17)
  [1027] Cue the music, I'm happy. - (2007-01-09)
  [1153] Object Oriented Model - a summary of changes from PHP4 to PHP5 - (2007-04-18)
  [1217] What are factory and singleton classes? - (2007-06-04)
  [1535] OO PHP demonstration - comparing objects and more - (2008-02-08)
  [1682] Accounts in PHP - an OO demo - (2008-06-19)
  [1819] Calling base class constructors - (2008-10-03)
  [1820] Sorting objects in PHP - (2008-10-04)
  [1925] Introduction to Object Oriented Programming - (2008-12-06)
  [2160] PHP - getclass v instanceof - (2009-05-07)
  [2169] When should I use OO techniques? - (2009-05-11)
  [2171] Cleaning up redundant objects - (2009-05-11)
  [2172] PHP4 v PHP5 - Object Model Difference - (2009-05-11)
  [2380] Object Oriented programming - a practical design example - (2009-08-27)
  [2434] Abstract classes, Interfaces, PHP and Java - (2009-10-03)
  [2435] Serialization - storing and reloading objects - (2009-10-04)
  [2632] Shipping a test harness with your class in PHP - (2010-02-12)
  [2641] Object Oriented Programming in PHP - (2010-02-19)
  [2680] Static class members in PHP - a documented example - (2010-03-16)
  [2717] The Multiple Inheritance Conundrum, interfaces and mixins - (2010-04-11)
  [2741] What is a factory? - (2010-04-26)
  [2774] PHP - Object Oriented Design in use - (2010-05-21)
  [2921] Does copying a variable duplicate the contents? - (2010-08-14)
  [2922] Getting the OO design write - with PHP a example - (2010-08-14)
  [3142] Private and Public - and things between - (2011-01-22)
  [3210] Catchable fatal error in PHP ... How to catch, and alternative solutions such as JSON - (2011-03-22)
  [3211] Computer Graphics in PHP - World (incoming data) to Pixel (screen) conversion - (2011-03-24)
  [3607] Designing your application - using UML techniques - (2012-02-11)
  [3608] Design Patterns - what are they? Why use them? - (2012-02-12)
  [3609] How do classes relate to each other? Associated Classes - (2012-02-12)
  [3840] Autoload in PHP - (2012-08-17)
  [3841] Copying, duplicating, cloning an object in PHP - (2012-08-18)
  [3843] Caching Design Patterns - (2012-08-20)
  [3953] Objects in PHP - Revision - (2012-12-16)
  [4057] stdClass in PHP - using an object rather than an associative array - (2013-04-02)
  [4073] Learning about Object Orientation in PHP - a new set of examples - (2013-04-28)
  [4356] Object factories in C++, Python, PHP and Perl - (2014-12-19)
  [4366] Changing what operators do on objects - a comparison across different programming languages - (2014-12-26)
  [4626] Singleton design pattern - examples and uses - (2016-01-20)
  [4628] Associative objects - one object within another. - (2016-01-20)

H307 - PHP - Web2 and caching
  [1633] Changing a screen saver from a web page (PHP, Perl, OSX) - (2008-05-06)
  [1647] Exchange Rates - PHP with your prices in your users currency - (2008-05-19)
  [1733] memcached - overview, installation, example of use in PHP - (2008-08-02)
  [1812] Starting Ajax - easy example of browser calling up server data - (2008-09-27)
  [1813] Ajax - going Asyncronous and what it means - (2008-09-28)
  [1814] Javascript/HTML example, dynamic server monitor - (2008-09-28)
  [1926] Flash (client) to PHP (server) - example - (2008-12-06)
  [1995] Automated server heartbeat and health check - (2009-01-16)
  [2196] New Example - cacheing results in PHP for faster loading - (2009-05-24)
  [2321] Uploading and Downloading files - changing names (Perl and PHP) - (2009-08-04)
  [2545] Scraping content for your own page via PHP - (2009-12-21)
  [3029] PHP data sources - other web servers, large data flows, and the client (browser) - (2010-11-04)
  [3094] Setting your user_agent in PHP - telling back servers who you are - (2010-12-18)
  [3186] How to add a customised twitter feed to your site - (2011-02-27)
  [3458] On this day ... one PHP script with three uses - (2011-09-26)
  [3955] Building up from a small PHP setup to an enterprise one - (2012-12-16)
  [3999] Handling failures / absences of your backend server nicely - (2013-02-08)
  [4055] Using web services to access you data - JSON and RESTful services - (2013-03-29)
  [4075] Further recent PHP examples - (2013-04-28)
  [4106] Web server efficiency - saving repetition through caches - (2013-05-30)
  [4136] How do I post automatically from a PHP script to my Twitter account? - (2013-07-10)


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Some other Articles
What would the Wiltshire Council bus cuts mean for Melksham?
The story behind the bus cuts, and what they could mean
Making travel time useful time on public transport
Caching results in an object for efficiency - avoiding re-calculation
Where does Wiltshire bus subsidy money come from?
Campaigning for a sensible bus solution and not against anyone!
Rambling from Westbury
Frosty morning, beauty of Wiltshire
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This is a page archived from The Horse's Mouth at http://www.wellho.net/horse/ - the diary and writings of Graham Ellis. Every attempt was made to provide current information at the time the page was written, but things do move forward in our business - new software releases, price changes, new techniques. Please check back via our main site for current courses, prices, versions, etc - any mention of a price in "The Horse's Mouth" cannot be taken as an offer to supply at that price.

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