update banyak gambar php mysqli

halo, saya lagi ngerjain projek untuk tugas akhir soal sistem informasi geografis pemetaan perumahan, saya ada bermasalah di update banyak gambar, yang saya pengen adalah : kalau saya pilih gambar baru, gambarnya terupdate di database, kalau tidak, datanya tidak terupdate.

ini function ubahgambar nya :

function ubahgambarperum($data){
    global $conn;

    $gambarLama     = htmlspecialchars ($data["gambarLama"]);
    $gambar         = upload_perum();
    //cek apakah user pilih gambar baru atau tidak
    if( $_FILES['gambar']['error'] == 4){
        $gambar = $gambarLama;
    } else {
        $gambar;
    }

    return mysqli_affected_rows($conn);}

dan ini function upload gambarnya : 

function upload_perum() {
    global $conn;

    $sizeGambar = 10 * 1024 * 1024;
    $idPerum =  $_POST["id"];
    foreach($_FILES["gambar_perum"]["tmp_name"] as $x=>$tmp_name){
    $namaFile = $_FILES['gambar_perum']['name'][$x];
    $ukuranFile = $_FILES['gambar_perum']['size'][$x];
    $tmpName = $_FILES['gambar_perum']['tmp_name'][$x];
    $tipe_file = pathinfo($namaFile, PATHINFO_EXTENSION);
    $error = $_FILES['gambar_perum']['error'];

    // cek apakah gambar sudah di upload
    if ($error == 4){
        echo "
            <script>
                alert('Gambar belum dimasukkan!') 
            </script>
        ";
    return false;
    }

    $ekstensiGambarValid = array('jpg', 'jpeg', 'png');
    $ekstensiGambar = explode('.', $namaFile);
    $ekstensiGambar = strtolower(end($ekstensiGambar));

    if(!in_array($ekstensiGambar, $ekstensiGambarValid)){
        echo " 
            <script>
                alert('Format gambar tidak didukung!')
            </script>";
        return false;
    }

    if($ukuranFile > $sizeGambar){
        echo " 
            <script>
                alert('Ukuran gambar terlalu besar!')
            </script>";
        return false;
    }

    //ambil nama perumahan untuk dimasukkan sebagai nama gambar dari table tiperumah
    $namaPerum   = $_POST["nama_perum"];
    $selectPerum = query("SELECT * FROM perumahan_master WHERE id_perum = '$idPerum'")[0];
    $idPerum = $selectPerum["id_perum"];
    $namaPerum = $selectPerum["nama_perum"];

    // jika lolos pengecekan, gambar siap di upload
    // generate nama baru
    $namaFileBaru  = 'Perum'.'-'. $namaPerum . '-'. $x;
    $namaFileBaru .= '.';
    $namaFileBaru .= $tipe_file;

        move_uploaded_file($tmpName, '../img-perum/' . $namaFileBaru);
        $queryupdateGambar      =   "   UPDATE perum_gambar
                                    SET
                                    gambar_perum = '$namaFileBaru'
                                    WHERE id_perum = $idPerum";
        mysqli_query($conn, $queryupdateGambar);
    }
    return $namaFileBaru;
}

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