Just call $m->get the first time to populate $data, and don't call it again if you're just making updates:-
if (!count($data))
$data=$m->get('foo');
$data[]=array('id'=>134,'title'=>'My First Car','content'=>'I love my car');
$m->set('foo',$data,TRUE,0);
If you make $data global then you can reference it from other functions