Source

File: wp-includes/Requests/IDNAEncoder.php

protected static function digit_to_char($digit) {
		// @codeCoverageIgnoreStart
		// As far as I know, this never happens, but still good to be sure.
		if ($digit < 0 || $digit > 35) {
			throw new Requests_Exception(sprintf('Invalid digit %d', $digit), 'idna.invalid_digit', $digit);
		}
		// @codeCoverageIgnoreEnd
		$digits = 'abcdefghijklmnopqrstuvwxyz0123456789';
		return substr($digits, $digit, 1);
	}