函数、数组、循环 -

1.// 给定一个数组$arr = [23,3,45,6,78,8,34],筛选其偶数成员组成新的数组返回，请封装函数。```php
<?php
$arr = [23,3,45,6,78,8,34];

function shaixuan($arr){
foreach($arr as $k =>$v){
if($k % 2 == 0){
$newArr[]=$v;
}
}
return $newArr;
}
var_dump(shaixuan($arr));
?>

2. 尝试实现简单的计算器功能，语言不限制。
```php
<?php
 $num1 = $_GET['num1'] ?? '请输入第一个数';
 $num2 = $_GET['num2'] ?? '请输入第二个数';
 $ysf = $_GET['con'] ?? '请选择运算符';
 $result= '';
if (isset($ysf)){
    if ($ysf== '*'){
        $result = $num1 * $num2;
    }
    if($ysf == '/'){
        if($num2 != 0){
           $result = $num1 / $num2;
        }else{
            $result = '除数不能为零';
        }
    }
    if($ysf == '+'){
        $result =$num1 + $num2;
    }
    if($ysf == '-'){
        $result = $num1 - $num2;
        }
}
?>
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>计算器</title>
</head>
<body>
    <form action="" method="get">
        <input type="text" name= "num1">
        <br>
        <select  name="con">
            <option value="+">+</option>
            <option value="-">-</option>
            <option value="*">*</option>
            <option value="/">/</option>
        <input type="text" name= "num2" >
        <br>
        <input type="submit" value="计算">
        <br>
    </form>
</body>
</html>
<?= $result?>