Sorting only a part of object/array in PHP - php

Question

I've been struggling around this for a while now and can't seem to get the right algorithm.
What I want is to sort this:
$variable = '{
"0": {
"id": "0",
"code": "main_colour",
"label": "Main Colour",
"options": [{
"id": "825",
"label": "White",
"products": ["1", "2", "3"]
}, {
"id": "840",
"label": "Cream",
"products": ["3", "4", "5"]
}],
"position": "0"
},
"2": {
"id": "0",
"code": "size",
"label": "Size",
"options": [{
"id": "825",
"label": "S",
"products": ["1", "2", "3"]
}, {
"id": "840",
"label": "M",
"products": ["3", "4", "5"]
}],
"position": "0"
}
}';
And the output would be
$variable = '{
"0": {
"id": "0",
"code": "main_colour",
"label": "Main Colour",
"options": [{
"id": "840",
"label": "Cream",
"products": ["3", "4", "5"]
},{
"id": "825",
"label": "White",
"products": ["1", "2", "3"]
}],
"position": "0"
},
"2": {
"id": "0",
"code": "size",
"label": "Size",
"options": [{
"id": "840",
"label": "M",
"products": ["3", "4", "5"]
}, {
"id": "825",
"label": "S",
"products": ["1", "2", "3"]
}],
"position": "0"
}
}';
So basically it should be sorted using the label inside the "options" without affecting the other fields. I've been trying usort and tried different algorithms but to no avail.
Current code that sorts only the outside "label" and not the inner label:
function optionsSort($a, $b) {
return strcmp($a['options'][0]['label'], $b['options'][0]['options']['label']);
}
usort($variable, "optionsSort"));

Answer 1

Here's the code:
// your array
$variable = '{
"0": {
"id": "0",
"code": "main_colour",
"label": "Main Colour",
"options": [{
"id": "825",
"label": "White",
"products": ["1", "2", "3"]
}, {
"id": "840",
"label": "Cream",
"products": ["3", "4", "5"]
}],
"position": "0"
},
"2": {
"id": "0",
"code": "size",
"label": "Size",
"options": [{
"id": "825",
"label": "S",
"products": ["1", "2", "3"]
}, {
"id": "840",
"label": "M",
"products": ["3", "4", "5"]
}],
"position": "0"
}
}';
$a = json_decode($variable);
foreach ($a as $item) {
// sorting function
usort($item->options, function($a, $b) { return strcmp($a->label, $b->label); });
}