Positive integer encoding as uppercase letters

int2letters.php

/**
 * Encode positive integers as upper case (ASCII) letters
 * Encodes 0 as A, 25 as Z, 26 as AA, 51 as AZ, 52 as BA, 701 as ZZ, 702 as AAA... and so on
 * @param  int $int
 * @return string
 */
function int2letters($int) {

	$letters = '';

	while($int > 25) {
		$letters = chr( $int % 26 + 65 ) . $letters;
		$int = (int)floor($int / 26);
		$int--;
	}

	$letters = chr($int + 65) . $letters;

	return $letters;

}