if (!is_numeric($this->num2)) { die("<script>alert('第二个数不为数字!');history.go(-1);</script>"); } } function operate() { switch ($this->op) { case '+': $result = $this->num1 + $this->num2; break; case '-': $result = $this->num1 - $this->num2; break; case '*': $result = $this->num1 * $this->num2; break; case '/': if ($this->num2 == 0) { die("<script>alert('被除数不能为0!!');history.go(-1);</script>"); } $result = $this->num1 / $this->num2; break; default: } $this->res = $result; } } $answer = new Calculator($_POST['num1'], $_POST['op'], $_POST['num2']); $answer->operate(); $resu = $answer->res; echo '答案是:' . $resu;