How to store data in db in array form

How to store data in db in array form

i want to store my PHP values in db(mysql) in the form of array...
for example
$a=array{10,20,30,40};
i want to store this variable $a in to db in the array form like how it's
storing in array using index.
why i want to do this because in future i may have to perform update or
delete operation on the array values..
i know that it's possible to do this thing... but i don't know how to
implement this..
i searched about this topic but i didn't get proper answer....
Please suggest me how to do this things...