SELECT `COLUMN_NAME`
FROM `INFORMATION_SCHEMA`.`COLUMNS`
WHERE `TABLE_NAME` IN ('country', 'person')
    AND `COLUMN_NAME` LIKE 'name_%';

$result = $db->query('SELECT p.name_person, c.name_country FROM person AS p LEFT JOIN country as c ON (p.id_country=c.id_country)');
$fields = array_keys($result->fetch(PDO::FETCH_ASSOC));

$fields = $result->fetch(PDO::FETCH_ASSOC);

$result = $db->query('SELECT person.name_person, country.name_country FROM person LEFT JOIN country ON (person.id_country=country.id_country)');

    print_r(array_keys($result));