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($_POST["num1"])){ //如果第一个第一个操作数为空输出错误信息，并停止计算
echo "<font color='red'>第一个操作数不能为空</font>";
unset($_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($_POST["num2"])){ //如果第二个第一个操作数为空输出错误信息，并停止计算
echo "<font color='red'>第二个操作数不能为空</font>";
unset($_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='red'>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='4' align='center'>";
echo "计算结果:$num1 $oper $num2 = $sum";
echo "</td></tr>";
}
?>
</form>
</table>
</body>
</html>
Hot AI Tools
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Undress AI Tool
Undress images for free
Clothoff.io
AI clothes remover
Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!
Hot Article
Hot Tools
MinGW - Minimalist GNU for Windows
This project is in the process of being migrated to osdn.net/projects/mingw, you can continue to follow us there. MinGW: A native Windows port of the GNU Compiler Collection (GCC), freely distributable import libraries and header files for building native Windows applications; includes extensions to the MSVC runtime to support C99 functionality. All MinGW software can run on 64-bit Windows platforms.
Zend Studio 13.0.1
Powerful PHP integrated development environment
EditPlus Chinese cracked version
Small size, syntax highlighting, does not support code prompt function
mPDF
mPDF is a PHP library that can generate PDF files from UTF-8 encoded HTML. The original author, Ian Back, wrote mPDF to output PDF files "on the fly" from his website and handle different languages. It is slower than original scripts like HTML2FPDF and produces larger files when using Unicode fonts, but supports CSS styles etc. and has a lot of enhancements. Supports almost all languages, including RTL (Arabic and Hebrew) and CJK (Chinese, Japanese and Korean). Supports nested block-level elements (such as P, DIV),
WebStorm Mac version
Useful JavaScript development tools
