array_keys

array_intersect

Last updated: Fri, 18 May 2012

array_key_exists

(PHP 4 >= 4.0.7, PHP 5)

array_key_exists — Prüft, ob ein Schlüssel in einem Array existiert

Beschreibung

bool array_key_exists ( mixed $key , array $search )

array_key_exists() gibt TRUE zurück, wenn key in dem Array vorhanden ist. key kann jeder für einen Array-Index mögliche Wert sein.

Parameter-Liste

key: Der zu prüfende Wert.
search: Ein Array mit den zu prüfenden Schlüsseln.

Rückgabewerte

Gibt bei Erfolg TRUE zurück. Im Fehlerfall wird FALSE zurückgegeben.

Changelog

Version	Beschreibung
5.3.0	Diese Funktion arbeitet nicht mehr mit Objekten. property_exists() sollte in diesem Fall genutzt werden.

Beispiele

Beispiel #1 array_key_exists()-Beispiel


<?php
$search_array = array('erstes' => 1, 'zweites' => 4);
if (array_key_exists('erstes', $search_array)) {
    echo "Das Element 'erstes' ist in dem Array vorhanden";
}
?>

Beispiel #2 array_key_exists() vs. isset()

isset() gibt nicht TRUE zurück für Schlüssel eines Arrays, die zu einem NULL-Wert gehören, array_key_exists() tut dies hingegen.


<?php
$search_array = array('erstes' => null, 'zweites' => 4);

// Gibt false zurück
isset($search_array['erstes']);

// Gibt true zurück
array_key_exists('erstes', $search_array);
?>

Anmerkungen

Hinweis:
Für die Abwärtskompatibiliät kann der folgende veraltete Alias verwendet werden: key_exists()

Siehe auch

isset() - Prüft, ob eine Variable existiert und ob sie nicht NULL ist
array_keys() - Liefert alle Schlüssel oder eine Teilmenge aller Schlüssel eines Arrays
in_array() - Prüft, ob ein Wert in einem Array existiert
property_exists() - Prüft auf die Existenz einer Eigenschaft eiens Objektes bzw. einer Klasse

add a note User Contributed Notes
array_key_exists

david at madole dot net
06-Jul-2007 05:11


Regarding performance differences between isset() and array_key_exists(), the differences may be there, but the function are not always interchangable.



Note that when $a[1] = null then isset($a[1]) == false but array_key_exists(1, $a) == true

eidberger at jakota dot de
11-Jun-2007 10:14


Just wondered why array_key_exists() makes me a cpu-load of 85% while isset() only needs 35%.



Not a big thing for one time execution, but in my case it have to check 1-dimensional array with ~ 15.000 entries 100 times a second. My code checks a big array for existing entrys and updates them, if needed.



Hopes it helps somebody. Notice that on many other functions, which makes coding more comfortable at the cost of speed.

alishahnovin at hotmail dot com
28-May-2007 07:47


Seems the array_key_exists can't find a key in a multidimensional array...



Here's my fix...



<?php



function multi_array_key_exists($needle, $haystack) {

  foreach ($haystack as $key=>$value) {

    if ($needle==$key) {

      return true;

    }

    if (is_array($value)) {

      multi_array_key_exists($needle, $value);

    }

  }

  return false;

}



?>

php at ianco dot co dot uk
09-Apr-2007 10:58


array_key_exists is case sensitive (at least in PHP 4.3.9). To make a case-insensitive comparison you could use strtolower on both sides.

inker2576 at yahoo dot com
07-Mar-2007 05:01


Further research on this has turned up that the performance problems are a known, confirmed bug in PHP 5.1.x, and have been fixed in PHP builds after September 2006.  You can find the bug report here:  http://bugs.php.net/bug.php?id=38812



However, just because it's a fixed bug doesn't really change the conclusion.  If you're writing a script and there's any chance it could be used on a PHP 5.1.x server, you should still avoid this function and use isset() or some other kind of test if you want it to run efficiently.

serkan yersen
07-Feb-2007 01:01


marzetti.marco,

I fixed your function it's is more optimized and working better now.



function regex_array_keys($arr, $pattern){

   $results[] = false;



   if(!is_array($arr))

       return false;



   foreach($arr as $key => $val){

         if(!is_array($key))

       if(preg_match($pattern,$key))

              array_push($results,$key);

   }



   return $results;

}

brauliorossi at gmail dot com
25-Jan-2007 06:42


Matt and mikael dot knutsson at gmail dot com:



this outputs bool(true):



$ar = array ( 'outter' => array ( 'inner' => 1 ) );

var_dump(array_key_exists('inner', $ar['outter']));

mikael dot knutsson at gmail dot com
16-Dec-2006 07:50


You're right, I'm not sure what I did wrong since I had a problem where array_key_exists returned true, while

<?php

$keys = array_keys( $array );

var_dump( in_array( 'key', $keys ) );

?>

returned false. (Which does the exact same thing) I probably either messed up the array, or the order in one of the array calls.

I rewrote the entire section where I had this problem (which was probably a good idea anyway), so I don't have any demonstration code.

Matt
01-Dec-2006 10:50


mikael dot knutsson at gmail dot com:

I don't think it does, at least in PHP5?



For example, this outputs bool(false):



$ar = array ( 'outter' => array ( 'inner' => 1 ) );

var_dump(array_key_exists('inner', $ar));



So it doesn't actually check the inner array for the key 'inner'.

mikael dot knutsson at gmail dot com
25-Nov-2006 01:05


When dealing with multi-dimensional arrays, this function checks through all keys in the array, including the "child arrays" unlike the array_keys( array, $search ) function which would only check and return from the first level of keys.



Took me a couple of minutes to figure out what was wrong and I hope it helps some people when looking for the right function.

Mike Toppa
03-Aug-2006 07:43


At least in PHP 4.4.0, array_key_exists is inconsistently sensitive to different data types. For example, if your first argument is a double and the keys in your array are integers, array_key_exists will always return false. If you then cast the first argument to an integer, or even to a string, then you can successfully match. I haven't tested all the possibilities, to see when it'll tolerate different data types and when it won't, so the easiest and safest solution is to cast your first argument to match the data type of the keys.

ncurtis at cenicola-helvin dot com
09-Jul-2006 12:25


array_key_exists() does not check values in the key i wrote this function to check if a key in an array has a empty value as corresponds to values that return true for empty() an redirects to a page if specified otherwise returns false



<?php

function keysExists($array, $startingIndex, $redirectPage) {

    if(is_array($array)) {

        if (!empty($startingIndex)) {

            for ($i = 0; $i < $startingIndex; $i++) {

                next($array);

            }

        }

        while(list($key, $value) = each($array)) {

            if (empty($value)) {

                if (!empty($redirectPage)) {

                    header("Location: $redirectPage");

                } else {

                    return FALSE;

                }

            }

        }

    } else {

        return FALSE;

    }

}

?>

email me and let me no if you found this useful!

marzetti.marco at gmail.com
06-Jul-2006 11:44


Returns the keys in $arr matching $pattern in a regex



<?php



function regex_array_keys ( &$arr, $pattern ) {

    $results[] = false;

    if( !is_array( $arr ) )

        return false;

    

    while( !is_null( $key = key( $arr ) ) ) {

        

        if( preg_match( $pattern, $key ) )

            $results[] = $key;

        next($arr);

    }

    reset( $arr );

    



    return $results;

}



?>

09-May-2006 05:44


property_exists() does the same thing for object properties.

add a note

array_keys

array_intersect

Last updated: Fri, 18 May 2012