Converting exactly decimal to fraction

FractionHelper.php

class FractionHelper {

	/*
	 * https://en.wikipedia.org/wiki/Continued_fraction
	 * Using this format instead float number (0.001) to avoid inaccurate value
	 * https://stackoverflow.com/questions/812815/php-intval-and-floor-return-value-that-is-too-low
	*/
	const TOLERANCE = 1.e-4;

	const PATTERN_FROM_STRING = '#^(-?\d+)(?:(?: (\d+))?/(\d+))?$#';

	public static function decimal2Fraction($x) {

		if(is_null($x)) return null;
		if(floor($x) - $x == 0) return floor($x);
		$isNegative = $x < 0 ? -1 : 1 ;
		$x = abs($x);
		$tolerance = self::TOLERANCE;
		$h1 = 1; $h2 = 0;
		$k1 = 0; $k2 = 1;
		$b = 1/$x;
		do {
			$b = 1/$b;
			$a = floor($b);
			$aux = $h1; $h1 = $a*$h1+$h2; $h2 = $aux;
			$aux = $k1; $k1 = $a*$k1+$k2; $k2 = $aux;
			$b = $b-$a;

		} while (abs($x - $h1/$k1) >= ($x * $tolerance));
		$numerator = (int) $h1 * $isNegative;
		$denominator = (int) $k1;

		if ($numerator === $denominator) {
			return '1';
		}

		if (-1*$numerator === $denominator) {
			return '-1';
		}

		if (1 === $denominator) {
			return (string) $numerator;
		}

		if (abs($numerator) > abs($denominator)) {
			$whole = floor(abs($numerator) / $denominator);
			if ($numerator < 0) {
				$whole *= -1;
			}
			return sprintf('%d %d/%d',
				$whole,
				abs($numerator % $denominator),
				$denominator
			);
		}
		return sprintf('%d/%d',
			$numerator,
			$denominator
		);

	}

	public static function fractionString2Decimal($string) {

		if (preg_match(self::PATTERN_FROM_STRING, trim($string), $matches)) {
			if (2 === count($matches)) {
				// whole number
				return floatval($matches[1]);
			} else {
				// either x y/z or x/y
				if ($matches[2]) {
					// x y/z
					return (intval($matches[1]) + (intval($matches[2])/ intval($matches[3])) );
				}
				// x/y
				return  (intval($matches[1])/ intval($matches[3]));
			}
		}
		return floatval($string);
	}

}