Zend Framework 2 Validator for ABN's http://www.ato.gov.au/businesses/content.aspx?doc=/content/13187.htm

Abn.php

use Zend\Filter\Digits as DigitsFilter;
use Zend\Validator\AbstractValidator;

class Abn extends AbstractValidator
{
        const INVALID = 'invalidAbn';
	const DIGITS = 'digitsOnly';
	const INCORRECT_LENGTH = 'lengthMismatch';

	protected static $digitsFilter = null;

	protected $messageTemplates = [
		self::INVALID => 'Invalid ABN number',
		self::INCORRECT_LENGTH => 'ABN must be 11 characters long',
		self::DIGITS => 'ABN must only contain digits',
	];

	protected $weights = [10, 1, 3, 5, 7, 9, 11, 13, 15, 17, 19];

	public function isValid($value)
	{
		if (null === static::$digitsFilter) {
			static::$digitsFilter = new DigitsFilter();
		}
		$value = preg_replace('/\s/', '', (string) $value);
		$this->setValue($value);

		if ($this->getValue() !== static::$digitsFilter->filter($this->getValue())) {
			$this->error(self::DIGITS);
			return false;
		}
		if (strlen($this->getValue()) < 11) {
			$this->error(self::INCORRECT_LENGTH);
			return false;
		}
		$newNumber = 0;
		for ($i = 0; $i < strlen($value); $i++) {
			$number = (int)$value[$i];
			if ($i === 0) {
				$number--;
			}
			$newNumber += $number * $this->weights[$i];
		}
		if (is_int($newNumber/89)) {
			return true;
		}
		$this->error(self::INVALID);
		return false;
	}
}