1. 函數(shù)

function 函數(shù)名（參數(shù)類型:可選，參數(shù)）:返回值類型限定
{
函數(shù)體
return 返回值（返回任意類型，單個(gè)值，之后代碼不會(huì)執(zhí)行）；
}

//無(wú)返回值
function f1()
{
    return md5("abc");
}
echo f1(), "<hr>";

2. 函數(shù)返回值

2.1 返回指定類型

//返回指定類型
function f2($a, $b): int
{
    return $a + $b;
}
echo f2(1.1, 2.2), "<hr>"; //3

2.2 返回?cái)?shù)組

//返回?cái)?shù)組
function f3(): array
{
    return ['name' => 'Em', 'age' => 18];
}
$arr = f3();
print_r($arr);  //Array ( [name] => Em [age] => 18 )
echo '<hr>';

2.3 返回對(duì)象

//返回對(duì)象  以匿名類返回
function f4(): object
{
    return new class
    {
        public $id = '0001';
        public $gender = 'male';
    };
}
$user = f4();
var_dump($user);
//object(class@anonymous)#1 (2) { ["id"]=> string(4) "0001" ["gender"]=> string(4) "male" }
//訪問對(duì)象屬性
echo $user->gender; //male
echo '<hr>';

2.4 返回JSON字符串

//返回JSON字符串
function f5(): string
{
    global $arr;
    return json_encode($arr);
}
$jsonStr = f5();
echo $jsonStr; // {"name":"Em","age":18}
//解析JSON字符串，還原成PHP可以處理的數(shù)據(jù)類型
$jd = json_decode($jsonStr);
var_dump($jd);
//object(stdClass)#2 (2) { ["name"]=> string(2) "Em" ["age"]=> int(18) }
//JSON字符串解析為數(shù)組
$jd = json_decode($jsonStr, true);
var_dump($jd);
//array(2) { ["name"]=> string(2) "Em" ["age"]=> int(18) }

2.5 序列化字符串

//返回 序列化字符串
function f6()
{
    global $arr;
    return serialize($arr);
}
echo f6();
//a:2:{s:4:"name";s:2:"Em";s:3:"age";i:18;}
file_put_contents('f6.txt', f6());
//反序列化
var_dump(unserialize(f6()));
//array(2) { ["name"]=> string(2) "Em" ["age"]=> int(18) }

3. 參數(shù)

3.1 普通帶參數(shù)函數(shù)

# 循環(huán)創(chuàng)建表格
function createTable(int $row, int $col)
{
    $table = "<table border='1' cellspacing='0'>";
    for ($i = 0; $i < $row; $i++) {
        $table .= "<tr>";
        for ($j = 0; $j < $col; $j++) {
            $table .= "<td>1</td>";
        }
        $table .= "</tr>";
    }
    $table .= "</table>";
    return $table;
}
echo createTable(2, 3), '<hr>';

3.2 參數(shù)有默認(rèn)值

// 參數(shù)有默認(rèn)值
function createTable2(int $row = 2, int $col = 2)
{
    $table = "<table border='1' cellspacing='0'>";
    for ($i = 0; $i < $row; $i++) {
        $table .= "<tr>";
        for ($j = 0; $j < $col; $j++) {
            $table .= "<td>1</td>";
        }
        $table .= "</tr>";
    }
    $table .= "</table>";
    return $table;
}
echo createTable2(), '<hr>';

3.3 參數(shù)部分有默認(rèn)值，部分沒有默認(rèn)值

// 參數(shù)部分有默認(rèn)值，部分沒有默認(rèn)值
function createTable3(int $row, int $col, string $bgcolor = "lightblue", string $text = '?')
{
    $table = "<table border='1' cellspacing='0' bgcolor={$bgcolor}>";
    for ($i = 0; $i < $row; $i++) {
        $table .= "<tr>";
        for ($j = 0; $j < $col; $j++) {
            $table .= "<td>{$text}</td>";
        }
        $table .= "</tr>";
    }
    $table .= "</table>";
    return $table;
}
echo createTable3(5, 6), '<hr>';

3.4 引用參數(shù)

// 引用參數(shù)
function fo(&$p)
{
    return $p .= $p;
}
$v1 = '?';
echo fo($v1), '<br>';
echo $v1, '<hr>';

3.5 剩余參數(shù)

# 剩余參數(shù)
function getSum(...$params)
{
    return array_sum($params);
}
$arr = [1, 2, 3, 4, 5];
echo getSum(...$arr), '<hr>';    //15
echo getSum(1, 2, 3);    //6

4. 閉包/匿名函數(shù)

<?php
# 匿名函數(shù) 閉包
$closure = function ($name) {
    return 'name: ' . $name;
};
echo $closure('Em'), '<br>'; // name: Em
# 閉包通過use 可以訪問函數(shù)外部的自由變量/父作用域中的變量
$name = 'Em';
$age = 22;
$closure2 = function () use ($name, $age) {
    return sprintf('name: %s <br> age: %d', $name, $age);
};
echo $closure2(), '<br>';
//name: Em 
//age: 22
#閉包通過use引用傳遞
$closure3 = function ($newAge) use (&$age) {
    $age = $newAge;
};
$closure3(18);
echo $age, '<br>';  //18
#閉包常用作函數(shù)返回值
function foo($animal)
{
    return function ($sound) use ($animal) {
        return sprintf('%s: %s', $animal, $sound);
    };
}
echo foo('?')('meow~');

批改老師：滅絕師太

批改狀態(tài)：合格

老師批語(yǔ)：總結(jié)的很好, 你是怎么輸出可愛的小表情的呢