如何在不使用array_count_values（）的情况下创建数组？

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()?

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.

The best solution is to use array_count_values function. That counts frequency of values in an array. See this - http://php.net/manual/en/function.array-count-values.php

<?php
$array = array(1, "hello", 1, "world", "hello");
print_r(array_count_values($array));
?>
Array
(
    [1] => 2
    [hello] => 2
    [world] => 1
)

However, If you don't want to use that function, you can do an ugly way of for loop.

$arrayName = array(1,2,1,3,4,3,2,5);

$resultArray = array();
foreach($arrayName as $value) {
    $resultArray[$value] = isset($resultArray[$value]) ? $resultArray[$value] + 1 : 1;
}

print_r($resultArray); // Array ( [1] => 2 [2] => 2 [3] => 2 [4] => 1 [5] => 1 )