4月20日作业:

1. 举例演示函数的四种类型

//1.自定义函数
function userName():string
{
    return '程东旭';
}
echo userName();
//2.系统函数
echo '<hr>';
function aaa():int
{
    return time();
}
echo aaa();
//3.可变函数
echo '<hr>';
$type = 'email';
function email():string
{
    return 'admin@php.cn';
}
echo $type();
//4.匿名函数，闭包
echo '<hr>';
$max = function (int $a, int $b):int
{
    return max($a, $b);
};
echo $max(10, 20);

2. 举例演示函数多值返回的四种形式

//1.返回值是字符串
echo '<hr>';
function user():string
{
    $name = 'admin';
    $email = 'admin@php.cn';
    return $name . '的邮箱是' . $email;
}
echo user();
//2.返回值是数组
echo '<hr>';
function user1():array
{
    return ['程东旭', 30, 'chengdongxu@php.cn'];
}
$user1 = print_r(user1(), true);
printf('<pre>%s</pre>', $user1);
//3.返回值是json
echo '<hr>';
function user2():string
{
    return json_encode(['name' => 'chengdongxu', 'age' => 30, 'email' => 'chengdongxu@php.cn']);
}
$user2 = user2();
echo $user2;
//4.返回值是序列化
echo '<hr>';
function phone():string
{
    return serialize(['name' => 'apple phone', 'price' => 8000, 'color' => 'red']);
}
$phone1 = phone();
echo $phone1;
echo '<hr>';
//反序列化
$phone2 = unserialize(phone());
printf('<pre>%s</pre>', print_r($phone2, true));

3. 举例演示函数的四种参数

//1.值参数，仅传递值
$age2 = 30;
echo '<hr>';
function user4(int $age):int
{
    return $age += 2;
}
echo '我现在的年龄是' . user4($age2) . '<br>';
echo '我2年前的年龄是' . $age2 . '<br>';
//2.引用传递
echo '<hr>';
function user5(int &$age2):int
{
    return $age2 += 5;
}
$age3 = 30;
echo '我现在年龄是' . user5($age3) . '<br>';
echo '我现在年龄是' . $age3 . '<br>';
//3.默认参数
echo '<hr>';
function user6(int $a, int $b, string $opt = '*')
{
    $res = 0;
    switch ($opt) {
        case '+':
            $res = "$a + $b = " . ($a + $b);
            break;
        case '-':
            $res = "$a - $b = " . ($a - $b);
            break;
        case '*':
            $res = "$a * $b = " . ($a * $b);
            break;
        default:
            $res = '非法操作';
    }
    return $res;
}
echo user6(300, 200);
echo user6(300, 200, '+');
//4.剩余参数
echo '<hr>';
function user7()
{
    $num = 0;
    foreach (func_get_args() as $value){
        $num += $value;
    }
    return $num;
}
print_r(user7(1,5,55,66,33255,55,445,1));