I think you can use date() function to achive this
$date="19:24:15 06/13/2013";
echo date('h:i:s a m/d/Y', strtotime($date));
This will output
07:24:15 pm 06/13/2013
Live Sample
h is used for 12 digit time
i stands for minutes
s seconds
a will return am or pm (use in uppercase for AM PM)
m is used for months with digits
d is used for days in digit
Y uppercase is used for 4 digit year (use it lowercase for two digit)
Updated
This is with DateTime
$date = new DateTime('19:24:15 06/13/2013');
echo $date->format('h:i:s a m/d/Y') ;