A calculator based on a small program written in PHP basic language

A calculator based on a small program written in PHP basic language

Requirements: Enter numbers in the input box to perform addition, subtraction, multiplication, and division operations (html+php)

Ideas:

1 First, create the input numbers and operations In the input box of symbol, numbers use the text attribute of input, and operators use the option attribute of sellct.

2 Click the = sign in the input box to perform the corresponding operation.

3 The input box with the = sign can be done using the submit of input. , just click submit and the content in the form will be passed to php

4 Determine the operator obtained from the html and perform the corresponding operation

5 After the operation is completed, the result must be returned to the form (that is, assigning a value to the form)

Code

Html code

<form method="post" action=””>//method代表的表单的提交方式，本案例选的是post提交 action是接受的页面，为空表示提交到当前页
              <input type = "text" name="num1" >
              <select name = "select">
                     <option value="+" >+</option>
                     <option value="-" >-</option>
                     <option value="*" >*</option>
                     <option value="/" >/</option>
              </select>
              <input type = "text" name="num2" >
              <input type = "submit" name = "submit" value="=">
              <input type = "text" name="result" >
       </form>

PHP code

When the user clicks the submit button, the value will be passed through post. Now we need to accept the value in the form.

Make a few judgments before clicking

if (isset($_POST['submit'])) {
//isset检测变量是否设置,存在,或非NULL, 返回值为布尔, 如果变量存在返回true, 否则为false;，结合$_POST[“submit”], $_POST   //接收通过表单的method=’post’ 方法的传值
$num1 = $_POST['num1'];//获取第一个输入框中的值,通过input中的name属性获得
             $select = $_POST['select'];//同上
             $num2 = $_POST['num2'];//同上
       if (is_numeric($num1) && is_numeric($num2)) {
       //is_numeric() //检测变量是否为数字或数字字符串  返回值 ,true, false  如 100, ‘100’
 
             switch ($select) {//$select是前面传来的运算符
                    case '+'://根据switch的语法，case中的值和switch括号里的值相等那么就执行case后面的那句话，不等则继续往下找
                           $result = $num1+$num2;
                           break;
                    case '-':
                           $result = $num1-$num2;
                           break;
                    case '*':
                           $result = $num1*$num2;
                           break;
                    default:
                           if ($num2==0) {//加个判断，除数不能为0
                                  echo "<script>alert(&#39;输入的除数为0请重新输入&#39;)</script>";
                           }else{
                                  $result = $num1/$num2;
                                  break;
                           }     
             }
             }else{
                    //echo 当用户输入的不是数，可能是字符串则给用户提示
                    echo "<script>alert(&#39;输入的不是数&#39;)</script>";
                    $num1 = $num2 = $result = "";//把表单里的内容清空
             }
}

Screenshot of the running result

Screenshot when entering the correct number

After clicking the = sign

It means that the value is not passed to the form in html.

Now we have to set the value of the form

//Set the value of value to php The num value after operation lt;option value="-" >-< /option>

                                                                                  input type = "text" name="num2" value="" >

       

                                                                                                                                                                                                           ​The input box now has content when submitting the button, so when the user does not click the submit button, the value in the input box should be set to empty

Improve the code, add an else{

$num1 =$ at the end of the php code num2 = $result = "";

}

Screenshot

When clicking other operations, the middle operator is always +, screenshot

Code improvement

in html

< select name = "select">

                                          >+

/ /select has an attribute selected. When it is set, it is selected by default, so it must be compared with the value passed from php. True means it is selected, false means it is not selected.                               select == '-')echo 'selected'?>>-

>*

>/

截图看结果

当用户第一次进来

截图

说明要设置selecte中的默认值

代码

$select=”+”

基本功能已经完成

总的代码

<!DOCTYPE html>
<html>
<head>
       <meta charset="UTF-8">
       <title>Document</title>
</head>
<body>
       <?php
              if (isset($_POST[&#39;submit&#39;])) {
//isset检测变量是否设置,存在,或非NULL, 返回值为布尔, 如果变量存在返回true, 否则为false;，结合$_POST[“submit”], $_POST   //接收通过表单的method=’post’ 方法的传值
              $num1 = $_POST[&#39;num1&#39;];//获取第一个输入框中的值,通过input中的name属性获得
             $select = $_POST[&#39;select&#39;];//同上
             $num2 = $_POST[&#39;num2&#39;];//同上
       if (is_numeric($num1) && is_numeric($num2)) {
       //is_numeric() //检测变量是否为数字或数字字符串  返回值 ,true, false  如 100, ‘100’
 
             switch ($select) {//$select是前面传来的运算符
                    case &#39;+&#39;://根据switch的语法，case中的值和switch括号里的值相等那么就执行case后面的那句话，不等则继续往下找
                           $result = $num1+$num2;
                           break;
                    case &#39;-&#39;:
                           $result = $num1-$num2;
                           break;
                    case &#39;*&#39;:
                           $result = $num1*$num2;
                           break;
                    default:
                           if ($num2==0) {//加个判断，除数不能为0
                                  echo "<script>alert(&#39;输入的除数为0请重新输入&#39;)</script>";
                           }else{
                                  $result = $num1/$num2;
                                  break;
                           }     
             }
             }else{
                    //echo 当用户输入的不是数，可能是字符串则给用户提示
                    echo "<script>alert(&#39;输入的不是数&#39;)</script>";
                    $num1 = $num2 = $result = "";//把表单里的内容清空
             }
}else{
       $num1 = $num2 = $result = "";
       $select = "+";
}
        ?>
<form method="post" action=""><!-- //method代表的表单的提交方式，本案例选的是post提交 action是接受的页面，为空表示提交到当前页 -->
            <input type = "text" name="num1" value="<?php echo $num1?>"  >
              <select name = "select">
                     <option value="+" <?php if($select == &#39;+&#39;)echo &#39;selected&#39;?>>+</option>
                     <option value="-" <?php if($select == &#39;-&#39;)echo &#39;selected&#39;?>>-</option>
                     <option value="*" <?php if($select == &#39;*&#39;)echo &#39;selected&#39;?>>*</option>
                     <option value="/" <?php if($select == &#39;/&#39;)echo &#39;selected&#39;?>>/</option>
              </select>
              <input type = "text" name="num2" value="<?php echo $num2?>" >
              <input type = "submit" name = "submit" value="=">
              <input type = "text" name="result" value="<?php echo $result?>">
       </form>
</body>
</html>