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For 2021 - online Python 3 training - see ((here)).

Our plans were to retire in summer 2020 and see the world, but Coronavirus has lead us into a lot of lockdown programming in Python 3 and PHP 7.
We can now offer tailored online training - small groups, real tutors - works really well for groups of 4 to 14 delegates. Anywhere in the world; course language English.

Please ask about private 'maintenance' training for Python 2, Tcl, Perl, PHP, Lua, etc.
Static variables in PHP

When you call a function, you typically want a nice clean start with no "leftovers" from the previous call. And that's what you get by default in PHP. However, there can be exceptions where you want data to be retained and you can do that using:

EITHER a global variable which is shared with the main PHP script and retained throughout its run
OR a static variable which is retained by the function while your script is running, but is NOT shared with the main code.

The typical use of a static variable is in what we call an iterator - a function which steps through a series of results, generating the next value in the sequence each time it's called. Here is a code example:

<?php
$walrus = 77;
function nextmeal () {
   static $walrus = 0;
   $munch = array("fish","seagull","penguin","ice");
   $walrus++;
   $walrus %= count($munch);
   return $munch[$walrus];
   }
for ($k=0; $k<10; $k++) {
   print "What's for dinner - ".nextmeal()."?<br />";
   }
print $walrus; # Just to show you this is a different walrus!
?>


And here are the results:

What's for dinner - seagull?
What's for dinner - penguin?
What's for dinner - ice?
What's for dinner - fish?
What's for dinner - seagull?
What's for dinner - penguin?
What's for dinner - ice?
What's for dinner - fish?
What's for dinner - seagull?
What's for dinner - penguin?
77


You'll note that our Walrus gets a different meal each day, because the static variable $walrus within the nextmeal function is retained. But (just as a demonstration) the $walrus variable in the main code is set to 77 and remains at that value.

Full source code here and run it here. Further example [here]. Learn about it on a course run here.
(written 2007-10-05, updated 2010-12-31)

 
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
H105 - PHP - Functions
  [96] Variable Scope - (2004-10-22)
  [223] There is a function in PHP to do that - (2005-02-21)
  [308] Call by name v call by value - (2005-05-11)
  [339] Passing information into and out of PHP functions - (2005-06-07)
  [340] Code and code maintainance efficiency - (2005-06-08)
  [409] Functions and commands with dangerous names - (2005-08-11)
  [421] Don't repeat code - use loops or functions - (2005-08-21)
  [775] Do not duplicate your code - (2006-06-23)
  [866] A lazy programmer is a good programmer - (2006-09-15)
  [936] Global, Superglobal, Session variables - scope and persistance in PHP - (2006-11-21)
  [1021] PHP - static declaration - (2007-01-04)
  [1163] A better alternative to cutting and pasting code - (2007-04-26)
  [1202] Returning multiple values from a function (Perl, PHP, Python) - (2007-05-24)
  [1267] is there a lookup function in php? - (2007-07-15)
  [1357] Clean my plate, but keep my wine bottle. (PHP; Static) - (2007-09-18)
  [1784] Global - Tcl, PHP, Python - (2008-09-03)
  [2488] A variable number of arguments in a PHP function - (2009-11-02)
  [2630] Static variables and ampersands in PHP - (2010-02-10)
  [2682] Adding extensions to PHP Open Source applications - callbacks - (2010-03-17)
  [2737] Improving your function calls (APIs) - General and PHP - (2010-04-24)
  [2929] Passing a variable number of parameters in to a function / method - (2010-08-20)
  [3026] Coding efficiency - do not repeat yourself! - (2010-11-02)


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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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