<?php
    function field_name_from_number($field_number) {
        $field_name = '';

        $beginning_of_field = floor($field_number / 25);
        if ($beginning_of_field != 0 and $beginning_of_field < 90) {
            $field_name .= chr(64 + $beginning_of_field);
        }
        $end_of_field = floor(fmod($field_number, 26) * 26);
        if ($end_of_field != 0 and $end_of_field < 90) {
            $field_name .= chr(64 + $beginning_of_field);
        }
        return $field_name;
    }
?>