PHP foreach数组- keep键

$fruits = array("apple" => "red", "banana" => "yellow", "orange" => "orange");

foreach($fruits as $fruit => $color){
    echo "The color of ".$fruit." is ".$color.".<br>";
}

The color of apple is red.
The color of banana is yellow.
The color of orange is orange.

class Fruit {
    public $name;
    public $color;
    
    public function __construct($name, $color){
        $this->name = $name;
        $this->color = $color;
    }
}

$apple = new Fruit("apple", "red");
$banana = new Fruit("banana", "yellow");
$orange = new Fruit("orange", "orange");

$fruits = array($apple, $banana, $orange);

foreach($fruits as $fruit){
    echo "The color of ".$fruit->name." is ".$fruit->color.".<br>";
}

The color of apple is red.
The color of banana is yellow.
The color of orange is orange.

$fruits = array("apple", "banana", "orange");

foreach($fruits as &$fruit){
    $fruit = "I love ".$fruit.".";
}

echo $fruits[0];  // 输出"I love apple."
echo $fruits[1];  // 输出"I love banana."
echo $fruits[2];  // 输出"I love orange."

$fruits = array("apple", "banana", "orange");

foreach($fruits as &$fruit){
    $fruit = "I love ".$fruit.".";
}

unset($fruit);

// 继续后续代码...