Totalling elements of an associative array, using one of the keys

phpSimon

Hi everyone

I have an array, $list, like so

Array
(
    [0] => Array
        (
            [siteid] => 1
            [orderID] => 123456
            [ClientID] => JOHNS
            [ClientName] => John's Butchers
            [SalesType] => A
            [revenue] => Array
                (
                    [0] => Nil
                    [1] => Nil
                    [2] => 100
                )

    )

[1] => Array
    (
        [siteid] => 1
        [orderID] => 123457
        [ClientID] => JOHNS
        [ClientName] => John's Butchers
        [SalesType] => A
        [revenue] => Array
            (
                [0] => 200
                [1] => Nil
                [2] => Nil
            )

    )

[2] => Array
    (
        [siteid] => 2
        [orderID] => 123890
        [ClientID] => JOHNS
        [ClientName] => John's Butchers
        [SalesType] => B
        [revenue] => Array
            (
                [0] => 300
                [1] => Nil
                [2] => Nil
            )

    )

[3] => Array
    (
        [siteid] => 1
        [orderID] => 123234
        [ClientID] => BILLS
        [ClientName] => Bill's Bakers
        [SalesType] => C
        [revenue] => Array
            (
                [0] => Nil
                [1] => 175
                [2] => Nil
            )

    )

[4] => Array
    (
        [siteid] => 3
        [orderID] => 123479
        [ClientID] => TIMMYS
        [ClientName] => Timmy's Fruit & Veg
        [SalesType] => A
        [revenue] => Array
            (
                [0] => 250
                [1] => Nil
                [2] => Nil
            )

    )

The revenue array represents 3 months of values.

I want to reduce the entire array to a new one containing just the ClientID, name and the revenue array. The rest of the data can be ignored. If the ClientID exists more than once, the revenue should be summed for each month.

I've done this a really long-hand way. Does anyone have a suggestion of how to approach this in a neater way? Here's my current code assuming the above array exists in the variable $list;

	$totalarray = array();
	foreach($list AS $orderdetails){

	if (array_key_exists($orderdetails[ClientID], $totalarray)){ // this clientID is already in the new array
		// update the revenue array, summing in the new values
		$i=0;
		foreach($orderdetails[revenue] AS $value){
			$totalarray[$orderdetails[ClientID]][revenue][$i] = $totalarray[$orderdetails[ClientID]][revenue][$i] + $value;
			$i++;
		}

	}
	else{ // this clientID is not in the new array yet, add the values (and the client name)
		$totalarray[$orderdetails[ClientID]][ClientName] = $orderdetails[ClientName];
		$i = 0;
		foreach($orderdetails[revenue] AS $value){
			$totalarray[$orderdetails[ClientID]][revenue][$i] = $value;
			$i++;
		}


	}

}

Result array:

Array
(
    [JOHNS] => Array
       (

    [ClientName] => John's Butchers
    [revenue] => Array
        (
            [0] => 500
            [1] => Nil
            [2] => 100
        )
    )
[BILLS] => Array
   (
    [ClientName] => Bill's Bakers
    [revenue] => Array
        (
            [0] => Nil
            [1] => 175
            [2] => Nil
        )
    )
[TIMMYS] => Array
   (
    [ClientName] => Timmy's Fruit & Veg
    [revenue] => Array
        (
            [0] => 250
            [1] => Nil
            [2] => Nil
        )
    )
)

Thanks for your help.

johanafm

Most importantly! Turn on error reporting for all errors. Display them in development, log them in production.
Obvious, once the above is fixed: Get rid of all of these errors: E_NOTICE: Undefined constant constant_name, assumed 'constant_name'
```
# E_NOTICE error (but outputs the string "constant")
echo constant;

# no error, use this
echo 'constant';
```
1. I find isset to be easier to read which is why I'd use that instead of array_key_exist. Do note that they are not identical: isset returns false if the key exists but the value is null while array_key_exist returns true in this case. And isset is supposed to be faster should it matter.
2. Personal preference: if you need a counter, use a for-loop (not foreach).
3. If you want to sum and assign to the same variable again, use +=
  Especially if you have very long variable names
```
# compare…
$i_am_a_little_story['containing_another_little_essay']['or_history_of_payments'] = $i_am_a_little_story['containing_another_little_essay']['or_history_of_payments'] + $sum

# …with
$i_am_a_little_story['containing_another_little_essay']['or_history_of_payments'] += $sum;
```
  1. If you want to copy all array values to a new array, use direct assignment, as in
```
# use this
$newarray = $oldarray;

# not this
$newarray = array();
foreach($oldarray as $value)  {
    $newarray[] = $value;
}
```

phpSimon

Thank you very much, lots of interesting advice.

What do you find preferable about a for-loop when compared with foreach?

The variable names got long as a result of using longish key names in functions that return a lot of data in array format, so the += tip is brilliant.

Thanks again.

johanafm

phpSimon;11034515 wrote:
What do you find preferable about a for-loop when compared with foreach?

In general - nothing.

But in the particular case where you need both a counter from 0 .. [element_count - 1] and need to access a numerically indexed array, I personally find it easier to read the code on the form

for ($i = 0; count($arr['revenue']); ++$i) {
    $total[$clientId]['revenue'][$i] += $arr['revenue'][$i];
}

Using that form I directly see that they are both dealing with the same array indices, which it takes me just a few seconds to work out in the other case.
But there is no "true" better or worse with one over the other. Both work and both do the same thing. It's your code, which means stick with whatever form you find easier to read.

phpSimon;11034515 wrote:
The variable names got long as a result of using longish key names

Yeah I just did that to show the gain, not as critique in any way. Usually using descriptive names is a lot better in the long run than $a['cid']['r'][0]... since that tells you nothing 2 months from now. On the other hand, I sometimes use an extra variable or two to shorten it down in place

$ocid = $orderdetails['ClientID'];
foreach($orderdetails[revenue] AS $value){
    $totalarray[$ocid][revenue][$i] = $totalarray[$ocid]][revenue][$i] + $value;
    $i++;
}

which sometimes makes things a bit more readable, whithout actually hiding the original variable or key names.
[/code]
Thanks again.[/QUOTE]

NogDog

Remember that you can get the array key/index as part of a foreach():

$totalarray = array();
foreach($list  as $order) {
	if(!isset($totalarray [$order['ClientID']])) {
		$totalarray [$order['ClientID']] = array(
			'ClientName' => $order['ClientName'],
			'revenue' => $order['revenue']
		);
	}
	else {
		foreach($order['revenue'] as $key => $value) {
			$totalarray [$order['ClientID']]['revenue'][$key] += $value;
		}
	}
}