How do you check if an index exists in php?

(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 $key, array $array): bool

Parameters

Value to check.

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.

Examples

Example #1 array_key_exists() example

$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.

$search_array = array('first' => null, 'second' => 4);// returns false
isset($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

manhon824 at gmail dot com ¶

11 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.