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PHP : Function Reference : Array Functions : array_key_exists

array_key_exists

Checks if the given key or index exists in the array (PHP 4 >= 4.0.7, PHP 5)
bool array_key_exists ( mixed key, array search )

array_key_exists() returns TRUE if the given key is set in the array. key can be any value possible for an array index. array_key_exists() also works on objects.

Parameters

key

Value to check.

search

An array with keys to check.

Return Values

Returns TRUE on success or FALSE on failure.

Examples

Example254.array_key_exists() example

<?php
$search_array
= array('first' => 1, 'second' => 4);
if (
array_key_exists('first', $search_array)) {
echo
"The 'first' element is in the array";
}
?>


Note:

The name of this function is key_exists() in PHP 4.0.6.

Example255.array_key_exists() vs isset()

isset() does not return TRUE for array keys that correspond to a NULL value, while array_key_exists() does.

<?php
$search_array
= array('first' => null, 'second' => 4);

// returns false
isset($search_array['first']);

// returns true
array_key_exists('first', $search_array);
?>


Related Examples ( Source code ) » array_key_exists




Code Examples / Notes » array_key_exists

mikael dot knutsson

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.


diogoshaw

this function very good to use if you need to verify many variables:
<?php
function array_key_exists_r($keys, $search_r) {
$keys_r = split('\|',$keys);
foreach($keys_r as $key)
if(!array_key_exists($key,$search_r))
return false;
return true;
}
?>
e.g.
<?php
if(array_key_exists_r('login|user|passwd',$_GET)) {
// login
} else {
// other
}
?>
works for me, enjoy.
dg shaw.


alishahnovin

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;
}
?>


marzetti.marco

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;
}
?>


david

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


09-may-2006 04:44

property_exists() does the same thing for object properties.

matt

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'.


brauliorossi

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']));


serkan yersen

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;
}


eidberger

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.


lucknut dot xbl

I found this function very good to use if your want your urls like index.php?login or index.php?register
e.g.
<?php
if( array_key_exists( 'home',$_GET ) ) {
echo "Home - its where the heart is.";
} else if( array_key_exists( 'login',$_GET ) ) {
echo "Login code here!";
} else if( array_key_exists( 'register',$_GET ) ) {
echo "Register code here!";
} else {
echo "Home - its where the heart is.";
}
?>


sj-b

i dont like how empty() works.
an integer with value 0 or a boolean wth
value false (same like zero) counts as
empty too.
[code]function r_empty (&$check)
{
if (!isset($check)) return true;
if ($check == NULL) return true;
return false;
}[/code]
that is a good replacement for
both functions for me.


j_hattersleydykes {at} yahoo uk

hey - I thought this function maybe useful to someone somewhere..
It works on an array of the keys you want to check exist. you could pass in the names of form fields and the POST array - suppose it could be useful in aiding form validation.
function array_keys_exist(array $keys, array $toCheck, $whichKey = false)
{
foreach ($keys as $array_key)
{
if (! array_key_exists($array_key, $toCheck))
{
// return first key thats not found.
if ($whichKey)
{
return $array_key;
}
else
{
return false;
}
}
}
// all keys exist
return true;
}
hope someone finds it useful :)


albertid

Here my proposal for an "array_keys_exist":
function array_keys_exist($keys, $array)
{
 return (sizeof(array_diff(array_keys($array), $keys)) == 0);
}


inker2576

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.


mike toppa

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.

wolf550e

array_key_exists(), at least in 5.2.4, passes the array by value. I conclude this from seeing performance worsen as the array to search got bigger. isset() doesn't have this problem.

ncurtis

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!


php

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.

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