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一个简单的在线计算器

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May 25, 2016 pm 05:08 PM

php代码

<html>
    <head>
        <meta http-equiv="content-type" content="text/html; charset=utf8">
        <title>一个简单的计算器</title>
    </head>
    <body>
        <?php
            //如果用户单击了计算按钮才存在表单变量，才能接收表单数据和对数据进行验证
            //以下if语句判断是否将表单中的两个操作数提交到本页面，如果没有则不执行
            if(isset($_POST["num1"]) && isset($_POST["num2"])){
                if(empty($_POST["num1"])){  //如果第一个第一个操作数为空输出错误信息，并停止计算
                    echo "<font color=&#39;red&#39;>第一个操作数不能为空</font>";
                    unset($_POST["sub"]);   //取消表单中的提交变量，后面计算判断时将不执行
                }
                if(empty($_POST["num2"])){  //如果第二个第一个操作数为空输出错误信息，并停止计算
                    echo "<font color=&#39;red&#39;>第二个操作数不能为空</font>";
                    unset($_POST["sub"]);   //取消表单中的提交变量，后面计算判断时将不执行
                }
                $oper=$_POST["oper"];   //获取操作符号
                $num1=$_POST["num1"];   //获取第一个操作数
                $num2=$_POST["num2"];   //获取第二个操作数
                if($oper == "/"){
                    if($num2 == 0){
                        echo "<font color=&#39;red&#39;>0不能作为除数使用</font>";
                        unset($_POST["sub"]);
                    }
                }
            }
             
        ?>
        <!--以HTML表格的形式输出计算器的用户操作界面-->
        <table border="1" align="center" width="400">
            <form action="" method="post"> <!--使用POST方法提交给本页面-->
                <caption><h2>简单的计算器</h2></caption>
                <tr>
                    <td><input type="text" size="10" name="num1" value="<?php if(!empty($num1)){echo $num1;}?>"></td>
                    <td>
                        <select name="oper">
                            <option value="+" <?php if($oper == "+"){echo "selected";}?>>+</option>
                            <option value="-" <?php if($oper == "-"){echo "selected";}?>>-</option>
                            <option value="*" <?php if($oper == "*"){echo "selected";}?>>*</option>
                            <option value="/" <?php if($oper == "/"){echo "selected";}?>>/</option>
                        </select>
                    </td>
                    <td><input type="text" size="10" name="num2" value="<?php if(!empty($num2)){echo $num2;}?>"></td>
                    <td><input type="submit" name="sub" value="计算"></td>
                </tr>
                <?php
                    /**通过表单传过来的$_POST["sub]，判断是否单击了计算按钮
                    来决定以下计算是否执行以及是否输出计算结果**/
                    if(isset($_POST["sub"]) && !empty($_POST["sub"])){
                        $sum = 0; //声明一个存放计算结果的变量，初始值为0
                        echo $sum;
                        //使用switch语句，通过表单选择的操作符来决定执行哪种运算
                        switch($oper){
                            case "+":
                                $sum = $num1+$num2;
                                break;
                            case "-":
                                $sum = $num1-$num2;
                                break;
                            case "*":
                                $sum = $num1*$num2;
                                break;
                            case "/":
                                $sum = $num1/$num2;
                                break;
                        }
                        //以下的三行是在表格的新行中输出计算结果
                        echo "<tr><td colspan=&#39;4&#39; align=&#39;center&#39;>";
                        echo "计算结果:$num1 $oper $num2 = $sum";
                        echo "</td></tr>";
                    }
                ?>
            </form>
        </table>
    </body>
</html>