<form>
<input type="text" name="num1">
<input type="submit" value="计算">
</form>
<?php
$num1 =$_GET['num1'];
if(!is_numeric($num1)){
echo '请输入年份';
}
if($num1%4=0 && $num1%100!=0){
echo '闰年';
}
if($num1%400=0){
echo '闰年';
}
if($num1%4!=0 | $num1%400!=0){
echo '平年';
}
/*疑问：我在本地写了这个，保存为html打开之后表单在，但是点了计算之后是空白页面。请问是我保存的方式不对吗？应该如何保存文件*/
>
![[Web front-end] Node.js quick start](https://img.php.cn/upload/course/000/000/067/662b5d34ba7c0227.png)
Since it is the year, why do we need to use the is_numeric() function? The year should be an integer greater than 0
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保存为PHP文件。