array_key_exists

    (PHP 4 >= 4.0.7, PHP 5, PHP 7, PHP 8)

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

    Description

    array_key_exists(string|int|float|bool|resource|null $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.

    Parameters

    key

    Value to check.

    array

    An array with keys to check.

    Return Values

    Returns true on success or false on failure.

    Note:

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

    Changelog

    Version Description
    8.0.0 The key parameter now accepts bool, float, int, null, resource, and string as arguments.

    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";
    }
    ?>

    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);
    ?>

    Notes

    Note:

    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 is deprecated as of PHP 7.4.0, and removed as of PHP 8.0.0.

    To check whether a property exists in an object, property_exists() should be used.

    See Also

    • isset() - Determine if a variable is declared and is different than 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

    up
    6
    Rumour
    11 months 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]??[]) ;

    ?>
    up
    9
    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;
    }
    up
    -48
    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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