The PHP code is wrong. If you have ran that yourself, you would see it gives a parse error.
$json[]=array('label'=>$people['pi.name'].''.$people['pi.middle_name'].''.$people['ad1.address_name'], 'value'=>$people['pi.name'].''.$people['pi.middle_name'].''.$people['ad1.address_name']);
That code should fix it, for returning the correct json data. You missed the "," between the label and value.