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


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