将图像放入img标签中以使其对bootstrap响应

I have I picture in a variable like $image how could I put it in img tag ? the code is

$imgData = base64_encode($row->photo);

$img = "<img   src= 'data:image/jpeg;base64, $imgData'  />";

I show in page like this

echo '<div align="center">   '.$img.'   </div>';

I wont to put it in img tag to make it responsive like this

<img   src= '.$img.' class="img-responsive "/>