key()

(PHP 4, PHP 5, PHP 7)

从关联数组中取得键名

说明

key()返回数组中当前单元的键名。

参数

该数组。

返回值

key()函数返回数组中内部指针指向的当前单元的键名。但它不会移动指针。如果内部指针超过了元素列表尾部，或者数组是空的，key()会返回NULL。

更新日志

范例

Example #1key()例子

以上例程会输出：

fruit1
fruit4
fruit5

参见

• current() 返回数组中的当前单元
• next() 将数组中的内部指针向前移动一位
• foreach

Note that using key($array) in a foreach loop may have unexpected results. 
When requiring the key inside a foreach loop, you should use:
foreach($array as $key => $value)
I was incorrectly using:

and experiencing errors (the pointer of the array is already moved to the next item, so instead of getting the key for $value, you will get the key to the next value in the array)
CORRECT: 

Needed to get the index of the max/highest value in an assoc array.
max() only returned the value, no index, so I did this instead. 

(Editor note: Or just use the array_keys function)
Make as simple as possible but not simpler like this one :)
$k = array();
for($i = 0; $i 
In addition to FatBat's response, if you'd like to find out the highest key in an array (assoc or not) but don't want to arsort() it, take a look at this: