array 관련함수

array_search : 

http://php.net/manual/en/function.array-search.php

array_keys :
http://php.net/manual/en/function.array-keys.php

array_key_exists :
http://php.net/manual/en/function.array-key-exists.php 

in_array :
http://www.php.net/manual/en/function.in-array.php