Merging and adding values of 2 JSON feeds in PHP - arrays

Question

I'm trying to write a shopping list app for a website which already has ingredients listed in JSON.
The full code is at the bottom, but just to explain; What I'm aiming to do is to be able to merge the 2 arrays, adding the values from the 'quantity' when the 'name' (and preferably also the 'measure') matches.
e.g. 'Sunflower oil' is listed in both JSON feeds.
I want it to output as:
{"name":"Sunflower oil","quantity":110,"measure":"ml"}
but it currently overwrites the JSON and the output is:
{"name":"Sunflower oil","quantity":10,"measure":"ml"},
Any assistance in what I'm doing wrong would be greatly appreciated as JSON and objects/arrays aren't my strong point!
Thanks in advance - here's my code:
<?php
$a = '{"ingredients":[{"name": "Sunflower oil","quantity": 100,"measure": "ml"}]}';
$b = '{"ingredients":[{"name": "Sunflower oil","quantity": 10,"measure": "ml"},{"name": "Fennel seeds","quantity": 1,"measure": "teaspoon"},{"name": "Garlic","quantity": 1,"measure": "clove"}]}';
print_r( json_encode(array_merge(json_decode($a, true),json_decode($b, true))) );
?>

Answer 1

You can use the following code to get the expected result:
<?php
$a = '{"ingredients":[{"name": "Sunflower oil","quantity": 100,"measure": "ml"},{"name": "Olive oil","quantity": 50,"measure": "ml"}]}';
$b = '{"ingredients":[{"name": "Sunflower oil","quantity": 10,"measure": "ml"},{"name": "Fennel seeds","quantity": 1,"measure": "teaspoon"},{"name": "Garlic","quantity": 1,"measure": "clove"}]}';
$aArr = json_decode($a, true);
$bArr = json_decode($b, true);
$sumArr = array("ingredients" => array());
foreach ($aArr['ingredients'] as $valA) {
foreach ($bArr['ingredients'] as $keyB => $valB) {
if ($valA['name'] == $valB['name'] &&
$valA['measure'] == $valB['measure']) {
$valA['quantity'] += $valB['quantity'];
$sumArr['ingredients'][] = $valA;
unset($bArr['ingredients'][$keyB]);
continue 2;
}
}
$sumArr['ingredients'][] = $valA;
}
$sumArr['ingredients'] = array_merge($sumArr['ingredients'], $bArr['ingredients']);
print_r( json_encode( $sumArr ));
?>