Services, Mappers,
Models: Enterprise
Thinking in PHP
Aaron Saray - MKEPUG

Why trust this guy?
● 21 years:
programmer
● 12 years: internet
programmer
● PHP Design
Patterns - WROX
● Manager of Web
Team @ LPi
● So handsome

Disclaimer!!
I don't have a BS CS. But that doesn't matter.
Best practices exist in programming.
Not everyone programs the same way.
There is more than one way to solve a problem.
Understand the core concepts, don't get hung
up on the minutiae.
For every solution I have, you can do it a
different way too. Yours may work too!

What are we talking
about today?
● Services, Mappers, Models
○ Go by a few different names
○ Mix and max
● Future proofing our solutions
○ separation of concerns
○ enterprise thinking
● Making life easier by investments up front

What are Models?
● Represent a true entity in your business
○ user, visitor
○ box, ps3, blu-ray movie
● They know about themselves in their current state
○ they don't know if they're incomplete
○ they don't know how they're populated
● Do logic from the business
○ logical transformation that makes sense in your
realm

What are Models? (cont)
Examples:
● User:
○ first name, last name, age
■ calculates fullname
■ calculates user requires adult consent
● PS3
○ serial number, model number
■ calculates date manufactured from serial #

What are Models? (cont 2)
Out of the realm of model:
● Have I been saved to the database?
● Have I been created from a form input or a
MySQL result set?
● How can I get more information about
myself?

What are Mappers?
● Mappers map data to a model
● Mappers know about models. Models do not
know about mappers.
● Mappers are dependent on the data source
○ Swap data sources? Introduce a new mapper!

What are Mappers? (cont)
● Mapper interprets a request and creates a
corresponding call to MySQL
○ request for a package with ID #7, create MySQL call
for that, get results, apply to the model I received.
● Mapper applies data results to a model in
the proper way
● Mappers are very foreign to most
○ Most Frameworks provide generic ones with "magic"
○ Most custom code lacks mappers

What are Services?
● Services are the way that the rest of the
code requests objects
● Services know about a Model, and it's
corresponding Mapper. Models and
Mappers don't know about services.
● Services interpret requests, create new
models, and invoke mappers to populate
models.

What are Services? (cont)
● Services understand logical identifiers of
models
○ fetchById()
● Services can create containers or single
result sets
○ fetchPaginator(), fetchByEmail()
● Services retrieve and persist data
○ fetching / saving / updating

What are Services? (cont2)
● Services rarely change once created
○ Mappers change with new data sets
○ Models change with new logic
○ Retrieval methods are relatively stoic
○ Persistence methods CAN change more often

Show me an example!
Show User
Details for
User # 5
UserService::fetchById(5) new User();
UserMapper MySQL query
ID = 5
Yay!
Apply fetchAssoc to model

Example Code:
● It's easy for me to show you a perfect
situation
○ But unless you're making something brand new, it's
not really feasible
● Let's look at some novice PHP code
○ and refactor to Enterprise Thinking code!

What we're accomplishing?
● Will use MySQL to retrieve user information
● Want to show the full name, email address,
of user 5 on the screen
● Don't do this!

Controller Code

Class Code - Part 1

Class Code - Part 2

So What's Wrong
With This?
● From my introduction, you can spot some
things
● What are they?

Bad Things:
Seems like the User model is in charge of retrieving
data based off the ID

More Bad Things
I'm not sure if this data is
coming from the database -
where the rest is. It's a one-off
Yup, the user has to
populate itself, plus it
has to understand that
this is a key.

More Bad Things:
The model is now forever
tied to the data source,
and must be modified if it
changes.
Here logic is being done
The model is mapping itself to the data set results. in the model. That's fine.
If a data source is changed, even the creation of However, it's using map-
"full name" is lost. able data. :(

Save me!
● Model should be only concerned with itself
○ full name is logic
● Mapper should connect and retrieve MySQL
data and apply it to the model
● Service should be initialized in the controller
and retrieve the proper user of ID 5

A Simpler User Model
No population. Only stores data,
and calculations (see below).
Creating a full name is actually a logical calculation. For example,
American name, this is correct.
Latino heritage full name may contain multiple last names.

Mapper for MySQL
Only for MySQL - this is important!!
Mapper creates connection.
Mapper understands ID,
but has to receive a new
user instance. Can't
create one itself.
Retrieve data, and
apply it to the object.

User Service
Initialize a User
for the mapper.
Get new
mapper.
Send to
mapper the
user and the
data access
pointer
(user id).
Return the properly
populated model to
the requestor.

Updated Controller Code
Instead of creating a new
User object, create a
new service object.
Then, ask the service for
the user of ID #5.
Don't forget! The full
name is not really a
property - so now it's a
method call in our code.

What was gained?
● Model now only deals with business
information
● Service can easily ask for and interpret
requests for particular models
● Bound our mapper to MySQL
○ made it easier to swap out data sources

Ruh Roh!
● Requirements change!
● Choose your poison:
○ your boss said to new partner "it won't be a big deal,
of COURSE we can use your feed instead of our
database"
○ your client says "omg omg omg we now need to use
this feed because it's the newest thing do it now!"

Requirement Change:
Instead of using MySQL, now all user data
must be retrieved from a XML feed request.
Using a GET request, call the feed URL with a
parameter of the user ID.
You can expect an XML document with one
node with the attribute as the ID, and nodes for
the user information.

What We Used to
Have to Do
● Back in the day
○ Open up the User class and modify code
○ Possibly delete old code and lose it
○ Modify the model even though nothing has changed
○ Cry

What we will do now
● Create a new mapper class named after the
Remote XML feed
○ note: we don't have to get rid of any old code
■ what if boss changes his mind back?
● Change one line in Service class
● To summarize:
○ One line change of existing code
○ Rest is brand new code
■ SUCH A SMALL IMPACT

Fine: I did change the
controller
The only change is including the new file instead. A good
autoloader would have made this a non-issue. But, I had
to show you this. Ignore it as a required 'change'

One line change in Service
See? Simple
little change. If I
want to go back
to the old code, I
can change this
mapper back.

New Mapper Class
Same method
call, just
different data
retrieval and
preparation.

Final Thoughts
● Probably should create a mapper interface -
so that all mappers now have a mapFromId()
method
● It is easy to swap back and forth with
different data sources
● Business req changes are now easier
○ least impact on each individual part

The End
Aaron Saray
Milwaukee PHP Web Developer
Questions? http://aaronsaray.com
@aaronsaray