regex generator for range between two numbers in PHP

regex_range.php

<?php 
function regex_range($from, $to) {

	if($from < 0 || $to < 0) {
		throw new Exception("Negative values not supported"); 
	}

	if($from > $to) {
		throw new Exception("Invalid range $from..$to, from > to"); 
	}

	$ranges = array($from);
	$increment = 1;
	$next = $from;
	$higher = true;

	while(true) {

		$next += $increment;

		if($next + $increment > $to) {
			if($next <= $to) {
				$ranges[] = $next;
			}
			$increment /= 10;
			$higher = false;
		}
		else if($next % ($increment*10) === 0) {
			$ranges[] = $next;
			$increment = $higher ? $increment*10 : $increment/10;
		}

		if(!$higher && $increment < 10) {
			break;
		}
	}

	$ranges[] = $to + 1;

	$regex = '/^(?:';

	for($i = 0; $i < sizeof($ranges) - 1; $i++) {
		$str_from = (string)($ranges[$i]);
		$str_to = (string)($ranges[$i + 1] - 1);

		for($j = 0; $j < strlen($str_from); $j++) {
			if($str_from[$j] == $str_to[$j]) {
				$regex .= $str_from[$j];
			}
			else {
				$regex .= "[" . $str_from[$j] . "-" . $str_to[$j] . "]";
			}
		}
		$regex .= "|";
	}

	return substr($regex, 0, strlen($regex)-1) . ')$/';
}
?>