key

(PHP 4, PHP 5, PHP 7)

key — 从关联数组中取得键名

说明

mixed key ( array &$array )

key() 返回数组中当前单元的键名。

参数

array: 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 。

范例

Example #1 key() 例子

  <?php
$array  = array(
     'fruit1'  =>  'apple' ,
     'fruit2'  =>  'orange' ,
     'fruit3'  =>  'grape' ,
     'fruit4'  =>  'apple' ,
     'fruit5'  =>  'apple' );

 // this cycle echoes all associative array
// key where value equals "apple"
 while ( $fruit_name  =  current ( $array )) {
    if ( $fruit_name  ==  'apple' ) {
        echo  key ( $array ). '<br />' ;
    }
     next ( $array );
}
 ?>

以上例程会输出：

fruit1<br />
fruit4<br />
fruit5<br />

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

用户评论:

[#1] Anonymous [2014-11-26 21:14:16]

<?php function generarCodigo($longitud) { $key = ''; $pattern = '123456789ASKKDOQEMANDOASJDSO'; $max = strlen($pattern)-1; for($i=0;$i < $longitud;$i++) $key .= $pattern{mt_rand(0,$max)}; return $key; } echo generarCodigo(4) echo "-"; echo generarCodigo(4); echo "-"; echo generarCodigo(4); echo "-"; echo generarCodigo(4); ?>

[#2] art [2014-10-08 08:50:45]

Returns "Warning" message if given parameter is not an array.

[#3] lhardie [2014-04-23 16:05:14]

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:
<?php foreach($array as $value) {   $mykey = key($array); } ?>

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:
<?php
foreach($array as $key => $value)
{
  $mykey = $key;
}

A noob error, but felt it might help someone else out there.

[#4] vinob44 at gmail dot com [2013-10-23 11:43:31]

Suppose if the array values are in numbers and numbers contains `0` then the loop will be terminated. To overcome this you can user like this

<?php $array = array( '0' => '5', '1' => '2', '2' => '0', '3' => '3', '4' => '1'); // wrong approach while ($fruit_name = current($array)) { echo key($array).'<br />'; next($array); } // the way will be break loop when arra('2'=>0) because its value is '0', while(0) will terminate the loop // correct approach while ( ($fruit_name = current($array)) !== FALSE ) { echo key($array).'<br />'; next($array); } //this will work properly ?>

[#5] goker.cebeci [2012-02-23 19:41:04]

object usage:

<?php $object = new stdClass(); $object->child->key = 'value'; echo key((array) $object->child); // key ?>

[#6] FatBat [2011-10-17 12:20:49]

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.

<?php reset($x); // optional. arsort($x); $key_of_max = key($x); // returns the index. ?>

[#7] michael [2008-12-09 11:19:37]

Here is an improved version of the KeyName function below. It is simpler and faster, especially on large arrays as it runs in O(1) instead of O(n).

<?php function KeyName(array $a, $pos) { $temp = array_slice($a, $pos, 1, true); return key($temp); } ?>

Also, KeyName($a, -1) will return the last key, etc.

[#8] yarco dot w at gmail dot com [2007-09-13 01:45:42]

Re: br_joris[at]hotmail[doth]com

Do you really mean you want 2 keys point to 1 value?
What you've written seems you want 1 key point to 2 values.

But if you really want 2 keys point to 1 value, you could do the following:

<?php $buf['key1'] = 'abc'; $buf['key2'] = & $buf['key1']; ?>