DistintList.php

<?php
        //Enter your code here, enjoy!

$array = [1, 2, 2, 2, 3];

$newArray = [];
$dupCount = 0;
    
foreach($array as $el) {
    if(in_array($el, $newArray)) {
        $dupCount++;
    }
    $newArray[] = $el;
}

echo $dupCount;