The method year() is a helper routine that simplifies the creation of an oft-used SQL statement to obtain just the year of a specified date/time field as a 4 digit number (YYYY).

The date/time fieldname to be processed

/*
* To return an employee_no and the year of a date field,
* and sort by the hire date
 
*/
$sql = "SELECT emp_no, {$db->year('hire_date')} 
          FROM employees
          ORDER BY {$db->year('hire_date')}";
$data = $db->getAssoc($sql);