Changing date format

Hi, with the below code

echo '<div class="client"><span class="name">'.$testimonial->client_name.'</span>,<span class="post_date">'.$testimonial->post_date.'</span> <br/>';

the output will be “name,2013-08-19 18:35:47”

how can i change it to “name, 19 Aug 2013”??

please kindly help thank you!