PHP 7.3.14 Released

key

(PHP 4, PHP 5, PHP 7)

keyRetorna uma chave de um array

Descrição

key ( array &$array ) : mixed

key() retorna a chave da posição atual de um array.

Parâmetros

array

O array.

Valor Retornado

Retorna o índice.

Exemplos

Exemplo #1 Exemplo da key()

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

// este ciclo exibirá toda a chave do array associativo
// onde o valor é igual a "apple"
while ($fruit_name current($array)) {
    if (
$fruit_name == 'apple') {
        echo 
key($array).'<br />';
    }
    
next($array);
}
?>

O exemplo acima irá imprimir:

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

Veja Também

  • current() - Retorna o elemento corrente em um array
  • next() - Avança o ponteiro interno de um array

add a note add a note

User Contributed Notes 5 notes

up
342
lhardie
5 years ago
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.
up
48
vinob44 at gmail dot com
6 years ago
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
?>
up
11
FatBat
8 years ago
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.
?>
up
0
Md Tahazzot
1 month ago
(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; $i < count($arr); $i++){
    $k[$i] = key($arr);
    next($arr);
}
up
-4
danielmadsv at gmail dot com
10 months ago
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:

<?php

$arr
= [ '3' => 14, '1' => 15, '4' => 92, '15' => 65 ];

$key_of_max = array_search( max($arr) , $arr);

?>
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