Combine intersecting keys and values in 2 arrays - php

Question

I'm running through all of the array functions on php.net and unable to figure this out.
Essentially I want to take these two arrays:
Array
(
[0] => stdClass Object
(
[month] => October
[year] => 2015
[credit] => 1000.00
)
[1] => stdClass Object
(
[month] => September
[year] => 2015
[credit] => 200.00
)
)
Array
(
[0] => stdClass Object
(
[month] => October
[year] => 2015
[debit] => 2000.00
)
[1] => stdClass Object
(
[month] => August
[year] => 2015
[debit] => 50.00
)
)
...and have the output look like this:
Array
(
[0] => stdClass Object
(
[month] => October
[year] => 2015
[credit] => 1000.00
[debit] => 2000.00
)
[1] => stdClass Object
(
[month] => September
[year] => 2015
[credit] => 200.00
[debit] => 0
)
[2] => stdClass Object
(
[month] => August
[year] => 2015
[credit] => 0
[debit] => 50.00
)
)
I'm looked to merge "month" and "year" and combine the other keys, using a default value if the key doesn't exist. Any guidance?

Answer 1

Assuming $debits and $credits are the arrays shown in your question, I would approach it like this:
First loop over the credits, inserting them into the new "combined" array and adding a default value for debit as you go.
foreach ($credits as $credit) {
$credit->debit = 0.00; // provide a default value for debit
$combined[$credit->year . $credit->month] = $credit;
}
Then loop over the debits. Since there is the possibilities that entries will already be there from credits, there needs to be a check for this. This part should update existing values inserted from credits, or insert new values if there is no existing value.
foreach ($debits as $debit) {
if (isset($combined[$debit->year . $debit->month])) {
// update the debit if the entry already exists
$combined[$debit->year . $debit->month]->debit = $debit->debit;
} else {
// otherwise create a new entry with a default value for credit
$debit->credit = 0.00;
$combined[$debit->year . $debit->month] = $debit;
}
}
// If you need the results to be numerically indexed, you can use array_values
$numerically_indexed = array_values($combined);