Menampilkan Data dari Database ke Select2

gambar1.jpg

<div class="form-group">
  <label for="obat">Obat</label>
     <select id="obat" name="obat[]" class="form-control select2" multiple="multiple" style="width:500px">
        <?php
	$id = @$_GET['id'];
        $query = "SELECT * FROM tb_rm_obat WHERE id_rm='$id'";
	$sql = mysqli_query($con, $query) or die (mysqli_error($con));
	$data_rm_obat = mysqli_fetch_array($sql);
	?>
	<?php
	$sql_obat = mysqli_query($con, "SELECT * FROM tb_obat") or die (mysqli_error($con));
	while ($data_obat = mysqli_fetch_array($sql_obat)) {
	if ($data_rm_obat['id_obat']==$data_obat['id_obat']) {
	$select="selected";
	}else{
	$select="";
	}
	echo "<option $select>".$data_obat['nama_obat']."</option>";
	}
	?>
    </select>
</div>

pertnyaan saya data obat yg tampil di select2 hanya 1 data padahal saya input ada 3 data, tapi ketika saya mau edit datanya cuma tampil 1 ,mohon bantuannya