関連ワード:  php in_array array_key_exists    php in_array vs array_key_exists    php in_array vs array_key_exists performance    php multiple array key exists    php array_search vs array_key_exists    php array_key_exists vs isset    php array key exists multidimensional    php array_key_exists case insensitive    php check multiple array key exists    php array_key_exists vs isset performance