You'll want to explode the original date into its components, then format it using the date() function in conjunction with mktime()
Functions used:
date (format, timestamp)
mktime (hour,minute,second,month,day,year)
$dateparts = explode('/',$showdate);
$newdate = date( "jS F Y", mktime(0,0,0,$dateparts[1],$dateparts[0],$dateparts[2]) );
echo $newdate;
I think that'll do it.