PHP 유형 제약 조건에 대한 자세한 소개(코드 포함)

<?php

/**
 * 数组类型约束
 * @param array $arr
 */
function printArray(array $arr)
{
    echo implode(&#39;,&#39;, $arr);
}

printArray(array(1, 2, 3));// 1,2,3
printArray(&#39;1&#39;);// Fatal error: Uncaught TypeError: Argument 1 passed to printArray() must be of the type array, string given, called in D:\WWW\test.php on line 13 and defined in D:\WWW\test.php:7 Stack trace: #0 D:\WWW\test.php(13): printArray(&#39;1&#39;) #1 {main} thrown in D:\WWW\test.php on line 7

<?php

/**
 * 标量类型约束
 * @param string $name
 * @param int $age
 * @param float $height
 * @param bool $isBoy
 */
function sayInfo(string $name, int $age, float $height, bool $isBoy)
{
    echo &#39;姓名：&#39; . $name . &#39;，年龄：&#39; . $age . &#39;，身高：&#39; . $height . &#39;，是否为男孩：&#39; . ($isBoy ? &#39;是&#39; : &#39;否&#39;);
}

sayInfo(&#39;tom&#39;, 12, 134.5, true);// 姓名：tom，年龄：12，身高：134.5，是否为男孩：是

<?php

/**
 * 接口
 * Interface Human
 */
interface Human
{
    public function say();

    public function run();
}

/**
 * 实现 Human 接口
 * Class Boy
 */
class Boy implements Human
{
    public function say()
    {
        echo &#39;a boy say&#39;;
    }

    public function run()
    {
        echo &#39;a boy run&#39;;
    }
}

/**
 * 实现 Human 接口
 * Class Girl
 */
class Girl implements Human
{
    public function say()
    {
        echo &#39;a girl say&#39;;
    }

    public function run()
    {
        echo &#39;a girl run&#39;;
    }
}

<?php

include &#39;./human.php&#39;;

class Action
{
    /**
     * Boy 对象类型约束
     * @param Boy $boy
     */
    public function boySay(Boy $boy)
    {
        $boy->say();
    }

    /**
     * Girl 对象类型约束
     * @param Girl $girl
     */
    public function girlSay(Girl $girl)
    {
        $girl->say();
    }

    /**
     * Human 接口类型约束
     * @param Human $obj
     */
    public function humanRun(Human $obj)
    {
        $obj->run();
    }
}

$obj = new Action();
$obj->boySay(new Boy());// a boy say
echo '<br />';
$obj->girlSay(new Girl());// a girl say
echo '<br />';
$obj->humanRun(new Boy());// a boy run
echo '<br />';
$obj->humanRun(new Girl());// a girl run