What’s the difference between isset() and array_key_exists()? [duplicate]

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array_key_exists will definitely tell you if a key exists in an array, whereas isset will only return true if the key/variable exists and is not null.

$a = array('key1' => 'フーバー', 'key2' => null);

isset($a['key1']);             // true
array_key_exists('key1', $a);  // true

isset($a['key2']);             // false
array_key_exists('key2', $a);  // true

There is another important difference: isset doesn’t complain when $a does not exist, while array_key_exists does.

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