<?php
 
function hitungNomorBit($angka, $nomorBit) {
    if ($nomorBit !== 0 && $nomorBit !== 1) {
        return null;
    }
 
    $biner = [];
 
    if ($angka === 0) {
        $biner[] = 0;
    } else {
        while ($angka > 0) {
            $sisa = $angka % 2;
            array_unshift($biner, $sisa);
            $angka = (int)($angka / 2);
        }
    }
 
    $jumlah = 0;
    foreach ($biner as $bit) {
        if ($bit === $nomorBit) {
            $jumlah++;
        }
    }
 
    return $jumlah;
}
 
echo hitungNomorBit(13,0). "\n";
echo hitungNomorBit(13,1). "\n";
var_dump(hitungNomorBit(13,3));

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