<?phpclass Stack{  public $stack;  public $stack_top;  public function __construct(){    $this->stack=array();    $this->stack_top=-1;  }  public function push($data){    $this->stack[]=$data;    $this->stack_top++;  }  public function pop(){    if(!$this->is_empty())    {      $this->stack_top--;      return array_pop($this->stack);    }else    {      echo "stack is empty";    }  }  public function is_empty(){    if($this->stack_top==-1)    return true;  }}$string="1243-*+63/-";$arrs=str_split($string);echo var_export($arrs);$stack=new Stack();foreach($arrs as $arr){  switch($arr){    case "+":$one=$stack->pop();$two=$stack->pop();$temp=$two + $one;$stack->push($temp);break;    case "-":$one=$stack->pop();$two=$stack->pop();$temp=$two - $one;$stack->push($temp);break;    case "*":$one=$stack->pop();$two=$stack->pop();$temp=$two * $one;$stack->push($temp);break;    case "/":$one=$stack->pop();$two=$stack->pop();$temp=$two / $one;$stack->push($temp);break;    default:$stack->push($arr);  }}echo $stack->pop();?>

array ( 0 => '1', 1 => '2', 2 => '4', 3 => '3', 4 => '-', 5 => '*', 6 => '+', 7 => '6', 8 => '3', 9 => '/', 10 => '-',)1