在数组上使用 PHP 的空合并运算符

Question

我正在使用http://php.net/manual/en/migration70.new-features.php描述的 PHP 空合并运算符。

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Null coalescing operator \xc2\xb6\nThe 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.\n\n<?php\n// Fetches the value of $_GET[\'user\'] and returns \'nobody\'\n// if it does not exist.\n$username = $_GET[\'user\'] ?? \'nobody\';\n// This is equivalent to:\n$username = isset($_GET[\'user\']) ? $_GET[\'user\'] : \'nobody\';\n\n// Coalescing can be chained: this will return the first\n// defined value out of $_GET[\'user\'], $_POST[\'user\'], and\n// \'nobody\'.\n$username = $_GET[\'user\'] ?? $_POST[\'user\'] ?? \'nobody\';\n?>\n

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我注意到以下内容不会产生我预期的结果，即添加一个值为“默认”的新phone索引。$params

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

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为什么不？

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Answer 1

您无需向 params 添加任何内容。您给定的代码只是生成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';

Answer 2

上面@mrks的正确答案可以缩短为：

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

RFC：空合并等于运算符