Return One Row from MySQL

Add limit 0,1 and for PHP 7 use mysqli

$query = "SELECT name,age FROM people WHERE uid = '2' LIMIT 0,1";
$result = mysqli_query($query);
$res = mysqli_fetch_assoc($result);

echo $res["age"]; 

If uid is your primary key, or it has a unique constraint, you can simply call mysql_fetch_row($res) once.

If you want to verify that you actually got a result, you can check if mysql_num_rows($res) == 1.