How do you get data from a MySQL database with PHP according to a method id?

For example if we have database named "users", and we need user information from table "user_info", which has next parameters: 'userId', 'userName','Name','Age'.
$sel = mysql_query("SELECT * FROM users.user_info WHERE userId='$methodId'"); $ar = mysql_fetch_array($sel);
echo "
User Id is:".$ar['userId'].", UserName: ".$ar['userName'].", Name: ".$ar['Name'].", Age: ".$ar['Age']."
";