Sort an JSON array based on array values

Question

I have a JSON array like this

$countries = [
        {
          "id": "1",
          "country_name": "Afghanistan",
        },
        {
          "id": "2",
          "country_name": "Albania",
        },
        {
          "id": "3",
          "country_name": "Algeria",
        },
        {
          "id": "4",
          "country_name": "American Samoa",
        }       
        ..
        ..
        ..
        {
          "id": "50",
          "country_name": "Zimbabwe",
        }
];

The following array contains, the list of countries that I need to sort to top

$top_countries = ['United States', 'United Kingdom', 'German'];

What is the best way to sort the above array as follows

$countries = [
        {
          "id": "30",
          "country_name": "United States",
        },
        {
          "id": "31",
          "country_name": "United Kingdom",
        },
        {
          "id": "20",
          "country_name": "German",
        },
        {
          "id": "1",
          "country_name": "Afghanistan",
        },
        {
          "id": "2",
          "country_name": "Albania",
        },
        {
          "id": "3",
          "country_name": "Algeria",
        },
        {
          "id": "4",
          "country_name": "American Samoa",
        }       
        ..
        ..
        ..
        {
          "id": "50",
          "country_name": "Zimbabwe",
        }
];

Without decode, I don't think php support to sort json, So, Decode json and convert to array, make necessary sorting operations and then again convert it to json. — Niraj Jani
– Niraj Jani, Commented Nov 27, 2015 at 12:19

Alex Blex · Accepted Answer · 2015-11-27 13:03:19Z

2

// index "value" of country by name
$top = array_flip($top_countries);

usort($countries, function($a, $b) use ($top) {
    // get "value" for each country, if it is in index
    $aValue = isset($top[$a->country_name])?$top[$a->country_name]:-1;
    $bValue = isset($top[$b->country_name])?$top[$b->country_name]:-1;

    if ($aValue == $bValue) {
        // preserve "original order", assuming they were ordered by id 
        return $a->id < $b->id ? -1 : 1;
    }
    return $aValue < $bValue ? 1:-1;
});

edited Nov 27, 2015 at 13:03

answered Nov 27, 2015 at 12:28

Alex Blex

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7 Comments

Asik Over a year ago

Great! it works! Please update your answer that need to reverse the array before flip it. :)

Asik Over a year ago

Also, change $a->country_name to $a['country_name']

Alex Blex Over a year ago

@Asik, I reverted 1 and -1 it in the return statement of the closure. It is cheaper than reverse $top_countries

Asik Over a year ago

Anyway, remaining countries orders are changed. I want to keep the remaining countries list order same.

Alex Blex Over a year ago

Inverting order of original array won't help. I updated the answer to maintain order for "non-top" countries.

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