Question

I have to create an application in PHP which will store the phone contacts of different users.

The table for storing the phone numbers is of the following format:

id,user-id,phone-number

Whenever an user tries to view all his contacts, first of all the contents from the cache should be shown and then the remaining ones from the database.

In implementing this, I have the following problem:

How to store the phone numbers in the cache? By this I mean what should be the key for inserting the phone numbers into memcache so that I can easily extract the data from it for any user. Remember, each user can have many phone numbers and there are many users.

Answer 1

the key should use user id

user id { mobile number ... + list of contact ...[which is the user id]} 
// by accessing this key able to get all mobile number
// and his contact list

suggestion value should be as simple as possible,
no JSON, no serialize data

user id {m:xxx,xxxx..., c:yyy,yyy,yyy}

this is to save spaces and also save processing for json_decode / unserailize

when getting all contacts for an user

1. fetch cache using user id (one call)
2. iterate the list of contact
3. fetch parellel of all the contact (user) key * function handling
4. iterate to build a multi dimensional array

when user adding/update/delete a mobile number,
or adding/update/delete a mobile number

1. fetch cache using user id (one call)
2. expire the key using user id
3. iterate the cache result

your function should be if cache not exist in memcache,
fetch from database,
set memcache,
return the database result