<body>
<table align="center" border=1 width=500>
<h2 align="center">计算器</h2>
<form action="jisuanqi.php" mothed="GET">
<tr>
<td>
<input type="text" name="num1" />
</td>
<td>
<select name="ysf">
<option value="+">+</option>
<option value="-">-</option>
<option value="×">×</option>
<option value="÷">÷</option>
</select>
</td>
<td>
<input type="text" name="num2" />
</td>
<td>
<input type="submit" name="sub" value="提交" />
</td>
</tr>
</form>
</table>
</body>
<?php
if(isset($_GET["sub"])){
$num1=$_GET["num1"]; //被除数
$num2=$_GET["num2"]; //除数
$ysf=$_GET["ysf"]; //运算符
$error=""; //错误信息
//检查各个参数是否正确
if($num1=="" || $num2==""){
$error="缺失参数！";
}elseif(!is_numeric($num1) || !is_numeric($num2)){
$error="参数错误！";
}else{
//选择不同的运算操作
switch($ysf){
case "+":
$result=$num1+$num2;
break;
case "-":
$result=$num1-$num2;
break;
case "×":
$result=$num1*$num2;
break;
case "÷":
if($num2=="0")
$error="零不能作为除数";
else
$result=$num1/$num2;
break;
}
}
//输出结果
echo "<table align='center' border=1 width=500><tr><td>";
if($error <> "")
echo $error;
else
echo "结果：".$num1.$ysf.$num2."=".$result;
echo "</td></tr></table>";
}
?>
</body>
此代码计算后，原位置不能显示输入的计算数值
优化后代码
<body>
<table align="center" border=1 width=500>
<h2 align="center">计算器</h2>
<form action="jisuanqi.php" mothed="GET">
<tr>
<td>
<input type="text" name="num1" value="<?php echo isset($_GET['num1']) && !empty($_GET['num1']) ? $_GET['num1'] : ''?>"/>
</td>
<td>
<select name="ysf">
<option value="+" <?php if(isset($_GET[ "ysf"]) && $_GET[ "ysf"]=="+" ){echo 'selected="selected"';} ?>>+</option>
<option value="-" <?php if(isset($_GET[ "ysf"]) && $_GET[ 'ysf']=='-' ){echo 'selected="selected"';} ?>>-</option>
<option value="×" <?php if(isset($_GET[ "ysf"]) && $_GET[ 'ysf']=='×' ){echo 'selected="selected"';} ?>>×</option>
<option value="÷" <?php if(isset($_GET[ "ysf"]) && $_GET[ 'ysf']=='÷' ){echo 'selected="selected"';} ?>>÷</option>
</select>
</td>
<td>
<input type="text" name="num2" value="<?php echo isset($_GET['num2']) && !empty($_GET['num2']) ? $_GET['num2'] : ''?>"/>
</td>
<td>
<input type="submit" name="sub" value="提交"/>
</td>
</tr>
</form>
</table>
<?php
if ( isset( $_GET[ "sub" ] ) ) {
$num1 = $_GET[ "num1" ]; //被除数
$num2 = $_GET[ "num2" ]; //除数
$ysf = $_GET[ "ysf" ]; //运算符
$error = ""; //错误信息
//检查各个参数是否正确
if ( $num1 == "" || $num2 == "" ) {
$error = "缺失参数！";
} elseif ( !is_numeric( $num1 ) || !is_numeric( $num2 ) ) {
$error = "参数错误！";
} else {
//选择不同的运算操作
switch ( $ysf ) {
case "+":
$result = $num1 + $num2;
break;
case "-":
$result = $num1 - $num2;
break;
case "×":
$result = $num1 * $num2;
break;
case "÷":
if ( $num2 == "0" )
$error = "零不能作为除数";
else
$result = $num1 / $num2;
break;
}
}
//输出结果
echo "<table align='center' border=1 width=500><tr><td>";
if ( $error <> "" )
echo $error;
else
echo "结果：" . $result;
echo "</td></tr></table>";
}
?>
</body>