!DOCTYPE html>
html>
 head>
 meta charset="UTF-8">
 title>php计算器/title>
 /head>
 body>
 form name="form" method="post" action="phpjisuan.php">
 请输入num1：input type="text" name="num1">/br>/br>
 请选择运算符：select name="sel">
    option value="+">+/option>
    option value="-">-/option>
    option value="*">*/option>
    option value="/">//option>
    option value="%">%/option>
    /select>/br>/br>
 请输入num2：input type="text" name="num2">/br>/br>
 input type="submit" name="Submit" value="计算">
   input type="reset" name="Reset" value="重置">
 /form>
 /body>
/html>

!DOCTYPE html>
html>
 head>
 meta charset="UTF-8">
 title>php计算器/title>
 ?php
   $num1=$_POST["num1"];
   $num2=$_POST["num2"];
   $sel=$_POST["sel"];
  ?>
 /head>
 body>
 ?php
 if($sel=="+"){
 $num=$num1+$num2;
 }
 else if($sel=="-"){
 $num=$num1-$num2;
 }
 else if($sel=="*"){
 $num=$num1*$num2;
 }
 else if($sel=="/"){
 if($num2!=0){
  $num=$num1/$num2;
 }else{
  echo "除数不能为0";
 }
 }
 
 else if($sel=="%"){
 if($num2!=0){
  $num=$num1%$num2;
 }else{
  echo "除数不能为0";
 }
 }
  
 if(isset($num)){
 echo "运算结果为$num";
 }
 ?>

 /body>
/html>