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array_key_exists

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

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

Description

array_key_exists ( mixed $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.

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Parameters

key

Value to check.

array

An array with keys to check.

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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.

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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);
?>

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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 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().

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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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Document created the 30/01/2003, last modified the 26/10/2018
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