bind_param

<?php
include('connect.php');
?>

<fieldset>
  <legend>Masukan Data</legend>
    <form action="tambah.php" method="post" enctype="multipart/form-data">
      Nama Sepeda :<input type="text" name="nama_sepeda">
      Size Sepeda :<input type="text" name="size_sepeda">
      Harga Sepeda:<input type="text" name="harga_sepeda">
      <input type="file" name="gambar">
      <input type="submit" name="tambah" value="Tambahkan">
    </form>
</fieldset>
<?php
if(isset($_POST['tambah'])){
$data = array (
              'nama_sepeda' => $_POST['nama_sepeda'],
              'size_sepeda' => $_POST['size_sepeda'],
              'harga_sepeda'=> $_POST['harga_sepeda'],
              'gambar' => $_FILES['gambar']['name'],
            );
$key = implode(",",array_keys($data));

$i=0;
foreach ($data as $key => $value) {
  if(is_int($value)){
    $nilaidata[$i] = $value;
  }else{
    $nilaidata[$i] = "'".$value."'";
  }
  $i++;
}
$hasilnilai = implode(",",$nilaidata);
$tempatgambar = $_FILES['gambar']['tmp_name'];
$namagambar = $_FILES['gambar']['name'];
move_uploaded_file($tempatgambar,"gambar/".$namagambar);

$query = $db->prepare("INSERT INTO sepeda ($key) VALUES (?)");
$query->bind_param('ssib',$hasilnilai);
$query->execute();

if($query){
  echo "data tersimpan";
}else{
  echo "data gagal tersimpan";
}

$query->close();
$db->close();
}
?>