PHP 数组映射
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PHP array mapping
提问by powtac
Is there a cleaner way than foreachto get an array of all "label" values?
有没有比foreach获取所有“标签”值的数组更清洁的方法？
$methods[0]['label'] = 'test';
$methods[0]['nr'] = 99;
$methods[1]['label'] = 'whatever';
$methods[1]['nr'] = 10;
foreach($methods as $method) {
$methodsLabel[] = $method['label'];
}
采纳答案by autonymous
As of PHP 5.5+, this is exactly what array_column()does:
从 PHP 5.5+ 开始，这正是array_column()它的作用：
$methodsLabel = array_column($methods, 'label');
http://php.net/manual/function.array-column.php
http://php.net/manual/function.array-column.php
3v4l example: https://3v4l.org/ZabAb
3v4l 示例：https://3v4l.org/ZabAb
回答by ircmaxell
No, there is no faster way than your implemented code. All other methods will be slower due to the overhead of a function call. For a small array the difference will be trivial, but for a large one (100 members or so, depending on implementation), the difference can be huge...
不，没有比您实现的代码更快的方法了。由于函数调用的开销，所有其他方法都会变慢。对于一个小数组，差异将是微不足道的，但对于一个大数组（100 个左右，取决于实现），差异可能很大......
You could array_mapit, but I'd stick with the raw PHP you posted above... It's easier to maintain and IMHO more readable...
你可以array_map，但我会坚持你在上面发布的原始 PHP ......它更容易维护，恕我直言更具可读性......
After all, tell me which at a glancetells you what it does more:
毕竟，告诉我哪个一目了然告诉您它的功能更多：
$results = array();
foreach ($array as $value) {
$results[] = $value['title'];
}
vs
对比
$results = array_map(function($element) {
return $element['title'];
},
$array
);
Or:
或者：
$callback = function($element) {
return $element['title'];
}
$results = array_map($callback, $array);
Personally, the first does it for me the best. It's immediately obvious without knowing anythingwhat it's doing. The others require knowledge of array_mapsemantics to understand. Couple that with the fact that array_mapisslower, and it's a double win for foreach.
就个人而言，第一个对我来说是最好的。这是不知道显而易见东西它在做什么。其他需要array_map语义知识才能理解。再加array_map上速度较慢的事实，对于foreach.
Code should only be as elegant as necessary. It should be readable above all else...
代码应该只在必要时尽可能优雅。它应该比其他一切都可读......
回答by Jacob Relkin
Sure, use array_map:
当然，使用array_map：
function getLabelFromMethod($method) {
return $method['label'];
}
$labels = array_map('getLabelFromMethod', $methods);
If you are on PHP 5.3+, you can also use a lambda function:
如果您使用的是 PHP 5.3+，您还可以使用 lambda 函数：
$labels = array_map(function($m) {
return $m['label'];
}, $methods);
回答by Gaurav
array_map('array_shift', $methods);
Here assumption is that label will be the first element of each array.
这里假设标签将是每个数组的第一个元素。
回答by efritz
On PHP 5.3+ you can use an anonymous function paired with array_map.
在 PHP 5.3+ 上，您可以使用与 array_map 配对的匿名函数。
$methodsLabel = array_map(function($item) { return $item['label']; }, $methods);
回答by Ravi Hirani
If label is first element in array then "current" with array_mapwill work fine.
如果 label 是数组中的第一个元素，则带有array_map 的“当前”将正常工作。
array_map('current', $methods);
回答by Gary Thomas
Arrow functionshave been introduced into PHP 7.4, which makes this a little bit cleaner.
PHP 7.4 中引入了箭头函数，这使得它更简洁一些。
$methodsLabel = array_map(fn($x) => $x['label'], $methods)
