PHP 7.1.0 Released

key

(PHP 4, PHP 5, PHP 7)

keyRetorna uma chave de um array

Descrição

mixed key ( array &$array )

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

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User Contributed Notes 4 notes

up
185
lhardie
2 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
3
vincphil54800 at gmail dot com
2 months ago
If you want to return the key on an associative array to get the first occurence of this array for exemple and if you don't know the key of the element that you search, it's impossible to find it without create you're own fonction, you can use for example :

/**
     * Retourne la premiére clé/valeur d'un tableau (notament utile pour les tableaux associatifs)
     * @param array $tab un tableau
     * @param int $mode 0 => renvoie la premiére valeur du tableau, 1=> renvoie la premiére clé du tableau
     * @return mixed la premiére occurence d'un tableau
     */
    public static function firstKey($tab,$mode = 0)
    {
        foreach($tab as $key=>$values)
        {
            if(is_array($values))
            {
                self::firstKey($values);
            }
            if($mode == 0)
            {
                return $values;
            }
            elseif($mode == 1)
            {
                return $key;           
            }
        }
        return null;
    }
up
38
vinob44 at gmail dot com
3 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
15
FatBat
5 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.
?>
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