I'm sure there's some beautiful reg statement that will handle this for you, but here's one solution:
$string="my car is broken";
$words_ar = explode(" ",$string);
do
{
if ( preg_match( "/[:alnum:]r[:alnum:]/", current($words_ar)))
{
echo current($words_ar) . "<BR>";
// the key for this solution can be accessed by key($words_ar)
}
}
while(next($words_ar));