Implement simple formula parsing with a single operator

$string = "#data_1 / #data_2";
class operate{
	private $params;
	private $dataarray;
	private $result;
	private function getResult() {
		return $this->result;
	}

	private function setResult($result) {
		$this->result = $result;
	}

	private function getDataarray() {
		return $this->dataarray;
	}

	private function setDataarray($dataarray) {
		$this->dataarray = $dataarray;
	}

	private function getParams() {
		return $this->params;
	}

	public function setParams($params) {
		$this->params = $params;
	}

	private function add($data_1,$data_2){
		return $data_1+$data_2;
	}
	private function minus($data_1,$data_2){
		return $data_1-$data_2;
	}
	private function multiply($data_1,$data_2){
		return $data_1*$data_2;
	}

	private function divide($data_1,$data_2){

			return $data_1/$data_2;

	}
	private function stringtoarray(){
		$params = $this->getParams();
		$dataarray =  explode(" ", $params);
		$this->setDataarray($dataarray);

	}

	private function getpos($array){

		$pos = array();
		$nums = sizeof($array);
		for ($i=0;$i<$nums;$i++){
			if(!is_numeric($array[$i])){
				$pos[] = $i;
			}
		}
		return $pos;
	}
	private function getdividepos(){
		$array = $this->getDataarray();// ||$expressionarray
		$pos = array();
		$nums = sizeof($array);
		for ($i=0;$i<$nums;$i++){
			if($array[$i]=="/"){
				$pos[] = $i;
			}
		}
		return $pos;
	}
	private function iszero(){
		$dataarray = $this->getDataarray();
		//print_r($dataarray);
		$array = $this->getdividepos(); // ||$devidpos
		//print_r($array);
		$nums = sizeof($array);
		echo "iszero nums:".$nums."";
		if ($nums==0){
			$this->setResult(1);
		}else{
			for ($i=0;$i<$nums;$i++){
				$key = $array[$i]+1;
				//$key = $i + 1;
				echo "key :$key";
				//echo "data:".$dataarray[$key];
				$data = (int)($dataarray[$key]);
				echo "data:".$data."";
				if ($data==0){
					$this->setResult(0);
				}
				else {
					$this->setResult($data);
				}
			}
		}
	}

	public function main(){
		$this->stringtoarray();
		$dataarray = $this->getDataarray(); //array("#data_1","/","#data_2");
		print_r($dataarray);
		$dividepos = $this->iszero();
		$result = $this->getResult();
		echo "reslut:".$result."";
		if($result==0){
			return 0;
		}else{
			$operatepos = $this->getpos($dataarray);
			$nums = sizeof($operatepos);
			for($i=0;$i<$nums;$i++){
				$pos = $operatepos[$i];
				$operate = $dataarray[$pos];
				echo "operate:".$operate."";
				switch ($operate){
					case "+":
						$key1 = $pos - 1;
						$key2 = $pos + 1;
					 	$data_1 = $dataarray[$key1];
					 	$data_2 = $dataarray[$key2];
					 	$tempdata = $this->add($data_1, $data_2);
					 	return $tempdata;
					case "-":
						$key1 = $pos - 1;
						$key2 = $pos + 1;
						$data_1 = $dataarray[$key1];
						$data_2 = $dataarray[$key2];
						$tempdata = $this->minus($data_1, $data_2);
						return $tempdata;
					case "*":
						$key1 = $pos - 1;
						$key2 = $pos + 1;
						$data_1 = $dataarray[$key1];
						$data_2 = $dataarray[$key2];
						$tempdata = $this->multiply($data_1, $data_2);
						return $tempdata;
					case "/":
						$key1 = $pos - 1;
						$key2 = $pos + 1;
						$data_1 = $dataarray[$key1];
						$data_2 = $dataarray[$key2];
						$tempdata = $this->divide($data_1, $data_2);
						return $tempdata;
				}


			}

		}


	}


}


$data_3 = "2 * 3";
$compute = new operate();
$compute ->setParams($data_3);
echo "result:".$compute->main();