PHP参考文献:一个理解

Question

我已经在我的旅程中看到了creaitng和构建我的一些php应用程序,vars,=和类名前面的&符号.

我知道这些是PHP参考资料,但我看过和看过的文档似乎并没有以我理解或混淆的方式解释它.你如何解释我见过的以下例子,使它们更容易理解.

  public static function &function_name(){...}

  $varname =& functioncall();

  function ($var, &$var2, $var3){...}

非常感激

Answer 1

假设你有两个函数

$a = 5;
function withReference(&$a) {
    $a++;
}
function withoutReference($a) {
    $a++;
}

withoutReference($a);
// $a is still 5, since your function had a local copy of $a
var_dump($a);
withReference($a);
// $a is now 6, you changed $a outside of function scope
var_dump($a);

因此，通过引用传递参数允许函数在函数作用域之外修改它。

现在是第二个例子。

你有一个返回引用的函数

class References {
    public $a = 5;
    public function &getA() {
        return $this->a;
    }
}

$references = new References;
// let's do regular assignment
$a = $references->getA();
$a++;
// you get 5, $a++ had no effect on $a from the class
var_dump($references->getA());

// now let's do reference assignment
$a = &$references->getA();
$a++;
// $a is the same as $reference->a, so now you will get 6
var_dump($references->getA());

// a little bit different
$references->a++;
// since $a is the same as $reference->a, you will get 7
var_dump($a);