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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 Our training notes are now very much out of date, but due to upward compatability most of our examples remain operational and even relevant ad you are welcome to make us if them "as seen" and at your own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))
PHP adding arrays / summing arrays

A question from my mailbox, answered in relation to our hotel. "I have a number of arrays in PHP and I want to add the elements of the arrays together". "There doesn't appear to be an array_sum function".

So in other words, my correspondent may have room occupancy data such as:

$bed1 = array(2,2,2,0,2,0,0);
$bed2 = array(1,1,1,1,1,0,0);
$bed3 = array(1,1,1,0,0,2,2);
$bed4 = array(0,0,0,0,0,0,0);
$bed5 = array(1,1,1,1,1,2,2);


and want to produce a report showing the nightly occupancy - perhaps to know how many breakfasts to prepare. What about

for ($k=0; $k<7; $k++) {
$occupancy[$k] = $bed1[$k]+$bed2[$k]+$bed3[$k]
+$bed4[$k]+$bed5[$k];
}


That code is horrid - it works with our 5 room place, but when we grow to 50 rooms ....

A good solution is to keep the data in an array of arrays - the "1", "2", "3" and so on in the variable names really should itself be a variable / subscript so that the summing can be done with a loop of loops:

$full = array($bed1,$bed2,$bed3,$bed4,$bed5);

combines the bedrooms and the the code to sum looks like:

for ($k=0; $k<7; $k++) {
$sm = 0;
for ($j=0; $j<count($full); $j++) {
$sm += $full[$j][$k];
}
$ot[$k] = $sm;
}


Which is slightly longer for my 5 rooms, but much MUCH shorter once we expand!

(See full source code here and run it here)
(written 2007-03-23, updated 2009-05-04)

 
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
H106 - PHP - Arrays
  [409] Functions and commands with dangerous names - (2005-08-11)
  [603] PHP - setting sort order with an associative array - (2006-02-13)
  [773] Breaking bread - (2006-06-22)
  [832] Displaying data at 5 items per line on a web page - (2006-08-14)
  [1199] Testing for one of a list of values. - (2007-05-22)
  [1451] More PHP sample and demonstration programs - (2007-12-01)
  [1614] When an array is not an array - (2008-04-17)
  [2215] If nothing, make it nothing. - (2009-06-02)
  [2274] PHP preg functions - examples and comparision - (2009-07-08)
  [2915] Looking up a value by key - associative arrays / Hashes / Dictionaries - (2010-08-11)
  [2920] Sorting - naturally, or into a different order - (2010-08-14)
  [3004] Increment operators for counting - Perl, PHP, C and others - (2010-10-18)
  [3379] Sorting data the way YOU want it sorted - (2011-08-05)
  [3534] Learning to program in PHP - Regular Expression and Associative Array examples - (2011-12-01)
  [4068] Arrays in PHP - contain different and even mixed data types - (2013-04-24)
  [4072] Splitting the difference with PHP - (2013-04-27)
  [4244] Disambiguation - PHP List - (2014-03-07)


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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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