PHP 获取数组中最后插入项的索引
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原文地址: http://stackoverflow.com/questions/3275082/
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PHP get index of last inserted item in array
提问by Christian
It's as easy as the title sounds; I need to get the index/key of the last inserted item. Why is this difficult? See the following two code samples:
就像标题听起来一样简单；我需要获取最后插入的项目的索引/键。为什么这很困难？请参阅以下两个代码示例：
$a=array();
echo 'res='.($a[]='aaa').' - '.(count($a)-1).'<br>';
echo 'res='.($a[]='bbb').' - '.(count($a)-1).'<br>';
echo 'res='.($a[]='aaa').' - '.(count($a)-1).'<br>';
die('<pre>'.print_r($a,true).'</pre>');
Writes:
写道：
res=aaa - 0
res=bbb - 1
res=aaa - 2
Array (
[0] => aaa
[1] => bbb
[2] => aaa
)
Sure, that seems to work fine, but see this:
当然，这似乎工作正常，但请看：
$a=array();
echo 'res='.($a[]='aaa').' - '.(count($a)-1).'<br>';
echo 'res='.($a[2]='bbb').' - '.(count($a)-1).'<br>';
echo 'res='.($a[]='aaa').' - '.(count($a)-1).'<br>';
die('<pre>'.print_r($a,true).'</pre>');
Writes:
写道：
res=aaa - 0
res=bbb - 1 <- wrong!
res=aaa - 2 <- wrong!
Array (
[0] => aaa
[2] => bbb <- real key
[3] => aaa <- real key
)
So in short, the popular workaround count($array)-1is flawed.
简而言之，流行的解决方法count($array)-1是有缺陷的。
回答by VolkerK
You can use key($a)together with end($a)
$a=array();
$a[]='aaa'; foo($a);
$a[3]='bbb'; foo($a);
$a['foo']='ccc'; foo($a);
$a[]='ddd'; foo($a);
function foo(array $a) {
end($a);
echo 'count: ', count($a), ' last key: ', key($a), "\n";
}
prints
印刷
count: 1 last key: 0
count: 2 last key: 3
count: 3 last key: foo
count: 4 last key: 4
回答by Sam152
You can use the end()function to get the last element in an array, and array_keys()to return an array of the array-keys. Confusing. In practice, it works like this:
您可以使用end()函数获取数组中的最后一个元素，并使用array_keys()返回数组键的数组。令人困惑。在实践中，它是这样工作的：
$key = end(array_keys($array));
Credit goes to hollsk in the comments.
在评论中归功于霍尔斯克。
回答by Pascal MARTIN
If you are only working with numerical indexes for your array, the last auto-generated index will always be the biggest array key of the array.
如果您只使用数组的数字索引，最后自动生成的索引将始终是数组的最大数组键。
So, for auto-generated indexes, using something like max(array_keys($a))should work.
因此，对于自动生成的索引，使用类似的方法max(array_keys($a))应该可行。
For example, this :
例如，这个：
$a=array();
echo 'res='.($a[]='aaa').' - '.(max(array_keys($a))).'<br>';
echo 'res='.($a[2]='bbb').' - '.(max(array_keys($a))).'<br>';
echo 'res='.($a[]='aaa').' - '.(max(array_keys($a))).'<br>';
die('<pre>'.print_r($a,true).'</pre>');
Would get you :
会让你：
res=aaa - 0
res=bbb - 2
res=aaa - 3
Array
(
[0] => aaa
[2] => bbb
[3] => aaa
)
But note that this will not work for situations when you are the one specifying the index...
但请注意，这不适用于您指定索引的情况...
回答by Christian
Bah, looks like I've found the answer by myself:
呸，看来我自己找到了答案：
$last_id = array_pop(array_keys($a));
回答by Christoph Diegelmann
On arrays with numeric keys from 0 to n-1 I always use:
在数字键从 0 到 n-1 的数组上，我总是使用：
$key = array_push($array, $value)-1;
It doesn't get any faster or simpler I guess. If someone got something like this that works for other arrays please let me know.
我猜它不会变得更快或更简单。如果有人有类似的东西适用于其他阵列，请告诉我。
