php - 为什么我需要 "&"？

Question

请参阅网络上有关 PHP 工厂模式的示例。

在 $kind =& Vehicle::category($wheel); 行中，我为什么要使用 &？

代码:

<?php
    class Vehicle {

        function category($wheel = 0) {
            if ($wheel == 2) {
                return "Motor";
            } elseif($wheel == 4) {
                return "Car";
            }
        }
    }

    class Spec {

        var $wheel = '';

        function Spec($wheel) {
            $this->wheel = $wheel;
        }

        function name() {
            $wheel = $this->wheel;
                return Vehicle::category($wheel);
        }

        function brand() {
            $wheel = $this->wheel;
                $kind =& Vehicle::category($wheel);
            if ($kind == "Motor") {
                return array('Harley','Honda');
            } elseif($kind = "Car") {
                return array('Nisan','Opel');
            }
        }
    }

    $kind = new Spec(2);
    echo "Kind: ".$kind->name();
    echo "<br>";
    echo "Brand: " . implode(",", $kind->brand());
?>

Answer 1

来自 Stack Overflow 问题 Reference - What does this symbol mean in PHP? :

=& 引用

• Reference assignment operator in PHP, =&
• What do the "=&" and "&=" operators in PHP mean?
• What do the '&=' and '=&' operators do?
• What does =& mean in PHP?

正如(已删除的)评论所说，最后一个链接应该适用于您的具体情况。