<body>
<?php
if (!empty($_POST)) {
$op=$_POST[‘point‘];
$sum1 = $_POST[‘sum1‘];
$sum2 = $_POST[‘sum2‘];
$sum = 0;
if ($sum1 != ‘‘ && is_numeric($sum1) && $sum2 != ‘‘ && is_numeric($sum2)) {
switch ($op) {
case ‘+‘:
$sum = $sum1 + $sum2;
break;
case ‘-‘:
$sum = $sum1 - $sum2;
break;
case ‘*‘:
$sum = $sum1 * $sum2;
break;
case ‘/‘:
$sum = $sum1 / $sum2;
break;
}
echo <<<shi
<script>
window.onload = function() {
document.getElementsByName(‘sum3‘)[0].setAttribute(‘value‘, ‘$sum‘)
document.getElementsByName(‘sum1‘)[0].setAttribute(‘value‘, ‘$sum1‘)
document.getElementsByName(‘sum2‘)[0].setAttribute(‘value‘, ‘$sum2‘)
document.getElementsByName(‘{$op}‘)[0].setAttribute(‘selected‘,‘selected‘)
}
</script>
shi;
} else {
echo ‘输入内容必须是数字‘;
}
};
?>
<form action="" method=‘post‘>
<input type="text" name="sum1">
<select name=‘point‘>
<option name=‘+‘>+</option>
<option name=‘-‘>-</option>
<option name=‘*‘>*</option>
<option name=‘/‘>/</option>
</select>
<input type="text" name=‘sum2‘>
<input type="submit" name=‘button‘ value=‘=‘>
<input type="text" name=‘sum3‘>
</form>
</body>
原文：https://www.cnblogs.com/shineguang/p/10964677.html