如何计算数组中键出现的值的数量

Question

I have an array like this

Array
(
 [0] => Array
    (
        [label] => A
        [uid] => 429
        [country_id] => 3
        [date] => 2015-02-11 13:55:34
        [DiffDate] => 20
    )

[1] => Array
    (
        [label] => A
        [uid] => 429
        [country_id] => 2
        [date] => 2015-02-11 13:55:34
        [DiffDate] => 20
    )
  ...... and so on
)

Now I have to calculate number of occurrences of country records example

country 1 has total 10 occurrence 
country 2 has total 20 occurrence

I need help as there are lot of arrays created also I am getting country id as different array

thanks in advance

Answer 1

There are a number of ways to tackle this. I like the following approach:

1. Restructure the array, so it's just a list of countries using array_column

   $countries = array_column($array, 'country_id');
   

or for PHP 5.4

    $countries = array_map(function($item) {
        return $item['country_id'];
    }, $array);

1. Use array_count_values to get the number of occurrences for each country

   $occurrences = array_count_values($countries);
   

---

Adding a country on a condition (alternative step 1)

If you need to do a check before adding the country to the $countries array, you're better of with a foreach loop than with array_map.

$countries = []
foreach ($array as $item) {
    if ($item['DiffDate'] >= 3) $countries[] = $item['country_id'];
}