如何在不使用array_count_values（）的情况下创建数组？

Question

I have an array, $arrayName = array(1,2,1,3,4,3,2,5);. I want the result as:

Array (
       [1] => 2
       [2] => 2
       [3] => 2
       [4] => 1
       [5] => 1
)

Without using array_count_values(), what is the logic behind array_count_values()?

Answer 1

This method will only loop each value once compared to other methods posted here.
Instead of looping the full array I get unique values and count them with array_keys and count.

$arrayName = array(1,2,1,3,4,3,2,5); 
$values = array_unique($arrayName);
Foreach($values as $val){
    $count[$val] = count(array_keys($arrayName, $val));
}

Var_dump($count);

https://3v4l.org/EGGJq

In your example I think my method may actually be slower than looping the full array, but if this was a large array there may be a benefit of not looping the full array.