key

(PHP 4, PHP 5, PHP 7)

keyPobiera klucz z tablicy asocjacyjnej

Opis

key ( array &$tablica ) : mixed

key() zwraza klucz bieżącego elementu z tablicy asocjacyjnej.

Przykład #1 Przykład użycia funkcji key()

<?php
$tablica 
= array(
    
'owoc1' => 'jabłko',
    
'owoc2' => 'pomarańcza',
    
'owoc3' => 'winogrono',
    
'owoc4' => 'jabłko',
    
'owoc5' => 'jabłko');

// poniższa pętla wyświetla wszystkie klucze w tablicy asocjacyjnej, gdzie
// wartość jest równa "jabłko"
while ($nazwa_owocu current($tablica)) {
    if (
$nazwa_owocu == 'jabłko') {
        echo 
key($tablica).'<br />';
    }
    
next($tablica);
}
?>

Patrz także: current() i next().

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User Contributed Notes 4 notes

up
329
lhardie
6 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
47
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
-1
danielmadsv at gmail dot com
1 year 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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