Array Map? Walk? Something Else? - php

Question

Thanks for all the inputs on the last two questions I asked. Slowly but surely, gettin there in terms of learning more. Now this next question has to do with array mapping/walking. I am not sure how to get this to work, but this is what's going on:
I have three arrays, each made up of keys with their own arrays. Each array looks like:
$arr1 = array(
'service3'=>array('price'=>'2.00','transit'=>'3'),
'service2'=>array('price'=>'4.00', 'transit'=>'1')
);
$arr2 = array(
'service1'=>array('price'=>'6.00','transit'=>'2'),
'service2'=>array('price'=>'8.00', 'transit'=>'1')
);
arr3 = array(
'service3'=>array('price'=>'2.00','transit'=>'3'),
'service2'=>array('price'=>'4.00', 'transit'=>'1')
);
and so on.
What I want to do is add the services from each of the three arrays with the matching keys. The caveats are that each array may be of a different length, and each may not have the same service (see above array 3 for what I mean).
I was looking for a cleaner way to add the three arrays together without running a bunch of foreach loops or creating temp arrays. It seems like array_map with a callback function would be a good way to go, or perhaps even array_walk. Just not sure how to proceed, because of the fact that the arrays may not be of the same length or even have the same service keys.

Answer 1

Here is a quick function, you can use (untested):
<?php
function group_by_service() {
$return = array();
$arrays = func_get_args();
foreach($arrays as $arr) {
foreach($arr as $service => $props) {
if (!array_key_exists($service, $return)) {
$return[$service] = $props;
} else {
$return[$service]['price'] += $props['price'];
$return[$service]['transit'] += $props['transit'];
}
}
}
return $return;
}
You can, then, use this function like this:
<?php
$arr1 = array(
'service3'=>array('price'=>'2.00','transit'=>'3'),
'service2'=>array('price'=>'4.00', 'transit'=>'1')
);
$arr2 = array(
'service1'=>array('price'=>'6.00','transit'=>'2'),
'service2'=>array('price'=>'8.00', 'transit'=>'1')
);
arr3 = array(
'service3'=>array('price'=>'2.00','transit'=>'3'),
'service2'=>array('price'=>'4.00', 'transit'=>'1')
);
$grouped = group_by_service($arr1, $arr2, $arr3);
print_r($grouped);