array_intersect
Something to keep in mind is that array_key_exists is case sensitive. So two things I'd like to say:
1. Could there be an additional option added on to the array_key_exists command so you can specify the case to be insensitive?
2. Here is how you can do this test in one command:
if( preg_match("/<key>/i", join(",", array_keys(<array>))) ){
<Do something>
}
But it would be a lot nicer to just have an additional option on the array_key_exists. Like so:
array_key_exists(<array>, ["i"] );
Ok - so why did this come up at all? I wrote a routine to convert any whacky UppERcAsE kind of lettering to just be lowercase letters. (ex: FgColorS becomes fgcolors and so forth.) So I never had to guess what the user was putting in to the program. There were two particular items (fgColors and bgColors) which I wanted to test against. If they were not supplied, my program would supply them. The above was the easiest way I could come up with to do this. :-)
array_key_exists
(PHP 4 >= 4.0.7, PHP 5)
array_key_exists — Checks if the given key or index exists in the array
Description
array_key_exists() returns TRUE if the given key is set in the array. key can be any value possible for an array index.
Parameters
- key
-
Value to check.
- search
-
An array with keys to check.
Return Values
Returns TRUE on success or FALSE on failure.
ChangeLog
| Version | Description |
|---|---|
| 5.3.0 | This function doesn't work with objetcs anymore, property_exists() should be used in this case. |
Examples
Example #1 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.
Example #2 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', $search_array);
?>
add a note
User Contributed Notesarray_key_exists
mmanning at mdanderson dot org
21-Oct-2008 05:13
21-Oct-2008 05:13
Karim Ratib
19-Aug-2008 02:09
19-Aug-2008 02:09
Here's a function to return a reference to the first array element that has a given key. The code works for multidimensional arrays:
<?php
function &array_find_element_by_key($key, &$form) {
if (array_key_exists($key, $form)) {
$ret =& $form[$key];
return $ret;
}
foreach ($form as $k => $v) {
if (is_array($v)) {
$ret =& array_find_element_by_key($key, $form[$k]);
if ($ret) {
return $ret;
}
}
}
return FALSE;
}
?>
jacobsingh at gmail dot com
17-Jun-2008 12:54
17-Jun-2008 12:54
I saw some examples above for array_keys_exist() or functions to see if multiple keys exist in a given array and return false if any of them don't.
Here is a simpler way to do this:
<?php
function array_keys_exist($keys,$array) {
if (count (array_intersect($keys,array_keys($array))) == count($keys)) {
return true;
}
}
$array = array ('filename' => 'myfile', 'filesize' => 1234, 'filepath' => '/tmp/myfile');
$keys = array('filename','filesize','filepath');
echo array_keys_exist($keys,$array);
//returns true
$keys[] = "somethingelse";
echo array_keys_exist($keys,$array);
//Returns false
?>
mankyd at gmail dot com
28-May-2008 07:29
28-May-2008 07:29
You'll notice several notes on this page stating that isset() is significantly faster than array_key_exists(). This may be true except for one small hitch. isset() will return false for arrays keys that have there value set to NULL, which is therefore not entirely accurate.
Example:
<?php
$foo = array();
$foo['bar'] = NULL;
var_dump(isset($foo['bar']));
var_dump(array_key_exists('bar', $foo));
?>
will output:
bool(false)
bool(true)
Be aware of this!
bplessingerMONKEYleapfroginteractive.com
30-Apr-2008 06:22
30-Apr-2008 06:22
I noticed that the function for recursion broke the ability to use this on objects, so I added another check to also allow it to work for objects.
<?php
function array_key_exists_r($needle, $haystack)
{
$result = array_key_exists($needle, $haystack);
if ($result)
return $result;
foreach ($haystack as $v)
{
if (is_array($v) || is_object($v))
$result = array_key_exists_r($needle, $v);
if ($result)
return $result;
}
return $result;
}
?>
tmont
29-Apr-2008 11:54
29-Apr-2008 11:54
The argument of array_key_exists() vs. isset() came up in the workplace today, so I conducted a little benchmark to see which is faster:
<?php
// one-dimensional arrays
$array = array_fill(0,50000,'tommy is the best!');
$arraykeyexists_result = array();
$start = microtime(true);
for ($i = 0; $i < 100000; $i++) {
if (array_key_exists($i,$array)) {
$arraykeyexists_result[] = 1;
}
else {
$arraykeyexists_result[] = 0;
}
}
$arrtime = round(microtime(true)-$start,3);
$start = microtime(true);
for ($i = 0; $i < 100000; $i++) {
if (isset($array[$i])) {
$arraykeyexists_result[] = 1;
}
else {
$arraykeyexists_result[] = 0;
}
}
$istime = round(microtime(true)-$start,3);
$totaltime = $arrtime+$istime;
$arrpercentage = round(100*$arrtime/$totaltime,3);
$ispercentage = round(100*$istime/$totaltime,3);
echo "array_key_exists(): $arrtime [$arrpercentage%] seconds\n";
echo "isset(): $istime [$ispercentage%] seconds\n";
?>
On Windows, the output is similar to
array_key_exists(): 0.504 [82.895%] seconds
isset(): 0.104 [17.105%] seconds
On Mac or Linux, isset() is faster but only by a factor of approximately 1.5.
Benjamin*removethis*BeckATgmx.de
08-Mar-2008 08:24
08-Mar-2008 08:24
Hi, i needed a recursive check is a key exists .. so here it is. I Hope it saves you time (-:
<?php
function array_key_exists_r($needle, $haystack)
{
$result = array_key_exists($needle, $haystack);
if ($result) return $result;
foreach ($haystack as $v) {
if (is_array($v)) {
$result = array_key_exists_r($needle, $v);
}
if ($result) return $result;
}
return $result;
}
$test = array(
"L0" => array(
"Über uns" => array(
"name" => "Über uns",
"MenuLast" => 0,
"subMenu" => 8,
"href" => "/admin/pages/admin_page_edit.php?nav_gid=1.1",
"navid" => 1.1,
"posid" => 1,
"klickPath" => 0,
),
"Was wir tun" => array(
"name" => "Über uns",
"MenuLast" => 0,
"subMenu" => 8,
"href" => "/admin/pages/admin_page_edit.php?nav_gid=1.1",
"navid" => 1.1,
"posid" => 1,
"klickPath" => 0,
),
),
);
dumpvar(array_key_exists_r('navid', $test), 'array_key_exists_r(\'navid\', $test)');
?>
Output:
var array_key_exists_r('navid', $test)(boolean): 'true'
packard_bell_nec at hotmail dot com
31-Jan-2008 06:46
31-Jan-2008 06:46
You can check whether a variable is defined by using array_key_exists()!
First, you may ask that no reserved array (would be called $LOCALS) is predefined in function scope (contrast to reserved array $GLOBALS in global scope. To solve it, you can use compact().
Then, you may ask that why property_exists() cannot be used. This is because no reserved function is predefined to create OBJECT containing variables and their values, and no reserved function is predefined to import variables into the current symbol table from an OBJECT. In addition, property_exists() breaks the naming convention of reserved function.
Finally, I show how to check whether a variable is defined by using array_key_exists():
<?php
function too(){
$roo = array_key_exists('foo', compact('foo'));
echo ($roo?'1':'0').'<br/>';
$foo = null;
$roo = array_key_exists('foo', compact('foo'));
echo ($roo?'1':'0').'<br/>';
}
too();
?>
The output will be:
0<br/>
1<br/>
mudsrcool at yahoo dot com
29-Dec-2007 01:19
29-Dec-2007 01:19
If you use func_get_args, you can make a slightly prettier implementation of diogoshaw's function:
<?php
function array_keys_exist() {
$keys = func_get_args();
$haystack = array_shift($keys);
foreach ($keys as $key)
if (!array_key_exists($key, $haystack)) return false;
return true;
}
//Pans out as:
if (array_keys_exist($_GET, 'login', 'user', 'passwd') {
//login;
} else {
//don't login;
}
?>
Erel Segal
13-Nov-2007 09:18
13-Nov-2007 09:18
array_diff can be very slow when the arrays are big. If all you need is to check which elements in array1 are not KEYS in array2, DON'T use:
<?php
array_diff($array1,array_keys($array2))
?>
A much quicker option is:
<?php
foreach ($array1 as $key=>$value) {
if (isset($array2[$key]))
unset($array1[$key]);
}
?>
On my computer, when $array1 has a single element and $array2 has 2600 elements, option 1 takes 50 milli-seconds, and option 2 takes 50 micro-seconds (1000 times less!).
wolf550e at gmail dot com
27-Sep-2007 09:51
27-Sep-2007 09:51
array_key_exists(), at least in 5.2.4, passes the array by value. I conclude this from seeing performance worsen as the array to search got bigger. isset() doesn't have this problem.
diogoshaw at gmail dot com
15-Sep-2007 08:58
15-Sep-2007 08:58
this function very good to use if you need to verify many variables:
<?php
function array_key_exists_r($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.
j_hattersleydykes {at} yahoo uk
27-Aug-2007 02:39
27-Aug-2007 02:39
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 $array_key;
}
else
{
return false;
}
}
}
// all keys exist
return true;
}
hope someone finds it useful :)
sj-b at hotmail dot de
01-Aug-2007 06:14
01-Aug-2007 06:14
i dont like how empty() works.
an integer with value 0 or a boolean wth
value false (same like zero) counts as
empty too.
[code]function r_empty (&$check)
{
if (!isset($check)) return true;
if ($check == NULL) return true;
return false;
}[/code]
that is a good replacement for
both functions for me.
Lucknut dot xbl at googlemail dot com
18-Jul-2007 07:44
18-Jul-2007 07:44
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.";
}
?>
david at madole dot net
06-Jul-2007 05:11
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, $a) == true
eidberger at jakota dot de
11-Jun-2007 10:14
11-Jun-2007 10:14
Just wondered why array_key_exists() makes me a cpu-load of 85% while isset() only needs 35%.
Not a big thing for one time execution, but in my case it have to check 1-dimensional array with ~ 15.000 entries 100 times a second. My code checks a big array for existing entrys and updates them, if needed.
Hopes it helps somebody. Notice that on many other functions, which makes coding more comfortable at the cost of speed.
alishahnovin at hotmail dot com
28-May-2007 07:47
28-May-2007 07:47
Seems the array_key_exists can't find a key in a multidimensional array...
Here's my fix...
<?php
function multi_array_key_exists($needle, $haystack) {
foreach ($haystack as $key=>$value) {
if ($needle==$key) {
return true;
}
if (is_array($value)) {
multi_array_key_exists($needle, $value);
}
}
return false;
}
?>
php at ianco dot co dot uk
09-Apr-2007 10:58
09-Apr-2007 10:58
array_key_exists is case sensitive (at least in PHP 4.3.9). To make a case-insensitive comparison you could use strtolower on both sides.
inker2576 at yahoo dot com
07-Mar-2007 05:01
07-Mar-2007 05:01
Further research on this has turned up that the performance problems are a known, confirmed bug in PHP 5.1.x, and have been fixed in PHP builds after September 2006. You can find the bug report here: http://bugs.php.net/bug.php?id=38812
However, just because it's a fixed bug doesn't really change the conclusion. If you're writing a script and there's any chance it could be used on a PHP 5.1.x server, you should still avoid this function and use isset() or some other kind of test if you want it to run efficiently.
serkan yersen
07-Feb-2007 01:01
07-Feb-2007 01:01
marzetti.marco,
I fixed your function it's is more optimized and working better now.
function regex_array_keys($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;
}
Matt
01-Dec-2006 10:50
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
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
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.