array_key_exists

(PHP 4 >= 4.0.7, PHP 5, PHP 7)

array_key_exists — Checks if the given key or index exists in the array

Descrierea

array_key_exists ( string|int $key , array $array ) : bool

array_key_exists() returns true if the given key is set in the array. key can be any value possible for an array index.

Parametri

key: Value to check.
array: An array with keys to check.

Valorile întoarse

Întoarce valoarea true în cazul succesului sau false în cazul eșecului.

Notă:
array_key_exists() will search for the keys in the first dimension only. Nested keys in multidimensional arrays will not be found.

Exemple

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";
}
?>

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);
?>

Note

Notă:
For backward compatibility reasons, array_key_exists() will also return true if key is a property defined within an object given as array. This behaviour should not be relied upon, and care should be taken to ensure that array is an array.

To check whether a property exists in an object, use property_exists().

A se vedea și

isset() - Determină dacă o variablă este declarată și diferă de null
array_keys() - Return all the keys or a subset of the keys of an array
in_array() - Checks if a value exists in an array
property_exists() - Checks if the object or class has a property

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User Contributed Notes 3 notes

down

Julian ¶

1 year ago


When you want to check multiple array keys: 

<?php

$array = [];
$array['a'] = '';
$array['b'] = '';
$array['c'] = '';
$array['d'] = '';
$array['e'] = '';

// all given keys a,b,c exists in the supplied array
var_dump(array_keys_exists(['a','b','c'], $array)); // bool(true)

function array_keys_exists(array $keys, array $array): bool
{
    $diff = array_diff_key(array_flip($keys), $array);
    return count($diff) === 0;
}

down

Rumour ¶

1 year ago


In PHP7+ to find if a value is set in a multidimensional array with a fixed number of dimensions, simply use the Null Coalescing Operator: ??

So for a three dimensional array where you are not sure about any of the keys actually existing

<?php

// instead of:
$exists = array_key_exists($key1, $arr) && array_key_exists($key2, $arr[$key1]) && array_key_exists($key3, $arr[$key1][$key2]) ;

// use:
$exists =  array_key_exists($key3, $arr[$key1][$key2]??[]) ;

?>

down

-39

manhon824 at gmail dot com ¶

13 years ago


I took hours for me to debug, and I finally recognized that,

You have to reset the $array before using array_key_exists 
reset($array);
array_key_exists($needle,$array);

Or you will get no reply.

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