如何根据值的实例数对数组进行排序？

Question

我想根据值的出现次数在php中对数组进行排序。

Array(Switzerland,Switzerland,Switzerland,Switzerland,Italy,Italy,Germany,France,France,France)

像这样......

Array(Switzerland,Switzerland, Switzerland,Switzerland,France,France,France,Italy,Italy,Germany,)

Answer 1

对于PHP7：

<?php

$couuntries = [
    'Switzerland',
    'Italy',
    'Switzerland',
    'France',
    'Switzerland',
    'Italy',
    'Germany',
    'France',
    'France',
    'Switzerland',
];
$counts = array_count_values($couuntries);
usort($couuntries, function($one, $second) use ($counts) {
    return $counts[$second] <=> $counts[$one];
});
print_r($couuntries);

输出：

Array
(
    [0] => Switzerland
    [1] => Switzerland
    [2] => Switzerland
    [3] => Switzerland
    [4] => France
    [5] => France
    [6] => France
    [7] => Italy
    [8] => Italy
    [9] => Germany
)

Answer 2

<?php

$someArray = ['aa','aa','b','ccc','ccc','ccc'];

$someArray = array_count_values($someArray); 
arsort($someArray); 
foreach($someArray as $key => $value) 
{
   for ($i = 0; $i<$value; $i++) $result[] = $key; 
}

print_r($result);
?>