在数组上使用PHP的空合并运算符

Question

我正在使用PHP的空合并运算符，该运算符在http://php.net/manual/en/migration70.new-features.php中有描述。

Null coalescing operator ¶
The null coalescing operator (??) has been added as syntactic sugar for the common case of needing to use a ternary in conjunction with isset(). It returns its first operand if it exists and is not NULL; otherwise it returns its second operand.

<?php
// Fetches the value of $_GET['user'] and returns 'nobody'
// if it does not exist.
$username = $_GET['user'] ?? 'nobody';
// This is equivalent to:
$username = isset($_GET['user']) ? $_GET['user'] : 'nobody';

// Coalescing can be chained: this will return the first
// defined value out of $_GET['user'], $_POST['user'], and
// 'nobody'.
$username = $_GET['user'] ?? $_POST['user'] ?? 'nobody';
?>

我注意到以下代码并没有产生我期望的结果，即在$params中添加一个新的phone索引，其值为"default"。

$params=['address'=>'123 main street'];
$params['phone']??'default';

为什么不呢？

- user1032531

Answer 1

您没有向参数中添加任何内容。您给出的代码只是生成了一个未使用的返回值：

$params['phone'] ?? 'default'; // returns phone number or "default", but is unused

因此，您仍然需要设置它：

$params['phone'] = $params['phone'] ?? 'default';

- mrks

Answer 2

上面来自@mrks的正确答案可以简化为：

    $params['phone'] ??= 'default';

RFC: Null Coalesce Equal 运算符

- Dmitry Bordun