What is 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. 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.
For More Information Please Refer:
https://www.php.net/manual/en/function.array-key-exists.php
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