如何在数组中找到第一个自由键 [英] How to find the first free key in an array

问题描述

我们都知道数组实际上是PHP中的有序树.鉴于此，数组索引(整数键)不必严格按照顺序排列，甚至根本不存在.因此，给定一个像这样的数组:

We all know that arrays are actually ordered trees in PHP. Given that, an array index (integer key) need not be in any strict order or even exist at all. So, given an array like:

array( 1 => 'A', 5 => 'B', 2 => 'C', 3 => 'D', 6 => 'E', 0 => 'F' )

如何在不重新索引数组的情况下确定第一个空键的最低整数(非负数)?在这种情况下，它将是4.

How can we determine the lowest (non negative) integer of the first empty key, without re-indexing the array? In this case it would be 4.

推荐答案

通过while循环轻松解决方案:

Easy solution by while loop:

function firstFreeKey($array)
{
  $i = 0;
  while(isset($array[$i])) $i++;
  return $i;
}

$array = array( 1 => 'A', 5 => 'B', 2 => 'C', 3 => 'D', 6 => 'E', 0 => 'F' );

echo firstFreeKey($array);

输出:

4

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