弹出键PHP中关联数组的值

问题描述

让S成为PHP中的关联数组，我需要从中检索并提取第一个元素(值和键).

Let S be an associative array in PHP, I need to retrieve and extract from it the first element, both the value and the key.

我会使用

value1=array_pop(S);

但这只会给我带来价值.

but it only gives me the value.

我可以使用

K=array_keys(S);
key1=array_pop(K);
value1=array_pop(S);

但是很复杂，因为它需要具有相同数据的两个副本.这是一个令人困惑的问题，因为数组本身就是数组数组中的一个元素.必须有一种更优雅的方法来在提取夫妇键/值的同时读取它.

but it is complicated because it requires to have two copies of the same data. WHich is a confusing since the array is itself an element in an array of arrays. There must be a more elegant way to just read the couple key/value while extracting it.

推荐答案

$value = reset($arr);
$key = key($arr);

(按此顺序)

请参见reset() ，key() .

unset($arr[$key]); # in case you want to remove it.

但是array_pop() 正在处理最后一个元素:

However array_pop() is working with the last element:

$value = end($arr);
$key = key($arr);
unset($arr[$key]); # in case you want to remove it.

请参见end() .

list($value, $key) = array(end($arr), key($arr));

或

extract(array('value'=>end($arr), 'key'=>key($arr)));

或

end($arr);
list($key, $value) = each($arr);

或您喜欢的任何游戏风格;)

or whatever style of play you like ;)

到目前为止，缺少处理空数组的方法.因此，需要检查是否存在最后一个(第一个)元素，如果没有，则将$key设置为null(因为null不能是数组键):

It was missing so far to deal with empty arrays. So it's a need to check if there is a last (first) element and if not, set the $key to null (as null can not be an array key):

for($key=null;$key===null&&false!==$value=end($arr);)
    unset($arr[$key=key($arr)]);

这将提供一个像$arr = array('first' => '1st', 'last' => '2nd.');这样的填充数组:

This will give for a filled array like $arr = array('first' => '1st', 'last' => '2nd.');:

string(4) "2nd." # value
string(4) "last" # key
array(1) { # leftover array
  ["first"]=>
  string(3) "1st"
}

还有一个空数组:

bool(false) # value
NULL # key
array(0) { # leftover array
}

是否害怕使用unset?

如果您不信任unset()具有所需的性能(尽管我没有运行任何指标，但我不认为这确实是一个问题)，可以使用本机array_pop()实现也是如此(但我真的认为unset()作为一种语言构造可能会更快):

Afraid of using unset?

In case you don't trust unset() having the performance you need (of which I don't think it's really an issue, albeit I haven't run any metrics), you can use the native array_pop() implementation as well (but I really think that unset() as a language construct might be even faster):

end($arr);
$key = key($arr);
$value = array_pop($arr);

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