bueno si he estado tratando de entender y al parecer ya sale
$cad = "Rafael Silva 34567 Hector Enriquez 12445";
$contactoRef = preg_replace("/[0-9]\b/e", 'nl2br("$0\r\n")', $cad );
y me los muestra
Rafael Silva 34567
Hector Enriquez 12445
www.tuxradar.com/practicalphp/4/8/5