Php Education Class (first Code)

Hi
I want to educate some PHP codes that i think they will be useful for all of you!

My 1st code is this:

<?phpclass calculator {		/**	 * Variable for holding all the numbers to add	 *	 * @var array	 */	private $numbers = array();		/**	 * Variable holding all the digits after the point	 *	 * @var array	 */	private $afterPoint = array();		/**	 * Maximum number of digits after the point	 * that a number has	 *	 * @var int	 */	private $afterPointLength = 0;		/**	 * Final result	 *	 * @var string	 */	private $result = 0;		/**	 * Constructor	 *	 */	public function __construct() {			}		/**	 * Adds a number to the list of numbers	 * to be summed	 *	 * @param string $number	 */	public function addNumber ($number) {		$this->numbers[] = (string)$number;	}		/**	 * Adds two numbers	 *	 * @param string $n1	 * @param string $n2	 * @return string	 */	private function doAdd ($n1, $n2) {				if ($n1 == 0) return $n2;		if ($n2 == 0) return $n1;				if (strlen($n1) <=13 && strlen($n2) <= 13) {			return (string)$n1+$n2;		}				$finalNumber = array();		$c = 0;				$n1 = (string)$n1;		$n2 = (string)$n2;				$m = max(strlen($n1), strlen($n2));		$n1 = str_pad($n1, $m, " ", STR_PAD_LEFT);		$n2 = str_pad($n2, $m, " ", STR_PAD_LEFT);				$numbers1 = chunk_split($n1, 13, ";");		$numbers1 = substr($numbers1, 0, -1);		$numbers1 = explode(";", $numbers1);		$numbers1 = array_reverse($numbers1);				$numbers2 = chunk_split($n2, 13, ";");		$numbers2 = substr($numbers2, 0, -1);		$numbers2 = explode(";", $numbers2);		$numbers2 = array_reverse($numbers2);				$maxSize = max(count($numbers1), count($numbers2));				for ($i=0;$i<$maxSize;$i++) {						$totalZeros  = 0;			$totalZeros1 = 0;			$totalZeros2 = 0;			for ($j=0;$j<strlen($numbers1[$i]);$j++) {				if ($numbers1[$i][$j] == 0) {					$totalZeros1++;				} else {					break;				}			}						for ($j=0;$j<strlen($numbers1[$i]);$j++) {				if ($numbers2[$i][$j] == 0) {					$totalZeros2++;				} else {					break;				}			}						$totalZeros = max($totalZeros1, $totalZeros2);						$partialResult = (string)($numbers1[$i] + $numbers2[$i] + $c);			$partialResult = str_pad($partialResult, strlen($partialResult)+$totalZeros, "0", STR_PAD_LEFT);			if (strlen($partialResult) > max(strlen($numbers1[$i]),strlen($numbers2[$i]))) {				$partialResult = (string)$partialResult;				$c = $partialResult[0];				$finalNumber[] = substr($partialResult, 1);			} else {				$c=0;				$finalNumber[] = $partialResult;			}		}		$finalNumber = array_reverse($finalNumber);		$finalNumber = implode("", $finalNumber);		if ($c != 0) $finalNumber = $c.$finalNumber;		return $finalNumber;	}		/**	 * Make the calculation	 *	 * @return string	 */	public function calc () {				for ($i=0; $i<count($this->numbers);$i++) {			$n = explode(".", $this->numbers[$i]);			if (count($n) == 1) {				$this->result = $this->doAdd($this->result, $this->numbers[$i]);			} elseif (count($n) == 2) {				$this->afterPoint[] = $n[1];				$this->afterPointLength = max($this->afterPointLength, strlen($n[1]));				$this->result = $this->doAdd($this->result, $n[0]);			} else {				trigger_error("<b>".$this->numbers[$i]."</b> is invalid !!", E_USER_ERROR);			}		}				if ($this->afterPointLength > 0) {			$r = 0;			foreach ($this->afterPoint as $number) {				$number = str_pad($number, $this->afterPointLength, "0", STR_PAD_RIGHT);				$r = $this->doAdd($r, $number);			}			if (strlen($r) > $this->afterPointLength) {				$this->result = $this->doAdd($this->result, substr($r, 0, -$this->afterPointLength));				if (strrpos($r, "0") != strlen($r)-1)					$this->result = $this->result.".".substr($r, 1);			} else {				$this->result = $this->result.".".$r;			}		}		return $this->result;	}}// example$calc = new calculator();// generate a very big numer$number  = "8347610948712974071265710983243861208762139437204172409821378273618976529283476109487129740712657109";$number = str_repeat($number, 10000);$calc->addNumber($number);$calc->addNumber($number);$time_start = microtime(true);$result = $calc->calc();$time_end = microtime(true);print "\nThe number has ".strlen($number)." digits. ";print "\nThe result has ".strlen($result)." digits. ";print "\nThe result is: ".$result;print "\nThe sum was executed in ".($time_end-$time_start)." seconds.";?>