“ A layer of mappers that moves data between objects and a database while keeping them independent of each other and the mapper itself” Martin Fowler, Patterns of Enterprise Application Architecture

Object-Relational Mapping (ORM) Objects => Relational Database Relational Database => Objects Think “Translation layer” Objects have no knowledge of database or SQL Database has no knowledge of objects Objects have no knowledge of mapper

Object-Relational Mapping (ORM)

Objects => Relational Database

Relational Database => Objects

Think “Translation layer”

Objects have no knowledge of database or SQL

Database has no knowledge of objects

Objects have no knowledge of mapper

Allows you to work with native objects in your application Writing SQL statements for everything in your application can be tedious INSERT, UPDATE especially Reduce time working on projects

Allows you to work with native objects in your application

Writing SQL statements for everything in your application can be tedious

INSERT, UPDATE especially

Reduce time working on projects

Ultra Portable No dependencies on packages outside PHP5 Use standard naming conventions Zend/PEAR Coding Standards Simple, clear syntax that fits with PHP Generic Usage Can work with any table by extending Eliminate the need for custom SQL (in most cases) Enable full automation wherever possible

Ultra Portable

No dependencies on packages outside PHP5

Use standard naming conventions

Zend/PEAR Coding Standards

Simple, clear syntax that fits with PHP

Generic Usage

Can work with any table by extending

Eliminate the need for custom SQL (in most cases)

Enable full automation wherever possible

Row objects as “dumb” as possible Not tied to the data mapper Allow custom SQL when needed for flexibility Support table relations Use adapters for database independence Don’t depend on too much “magic” No automatic discovery of tables or fields No table or column naming schemes for relations

Row objects as “dumb” as possible

Not tied to the data mapper

Allow custom SQL when needed for flexibility

Support table relations

Use adapters for database independence

Don’t depend on too much “magic”

No automatic discovery of tables or fields

No table or column naming schemes for relations

CodeIgniter DataMapper: http://stensi.com/datamapper/

What objects will we need to start? DataMapper Result – Individual row object Start with DataMapper Define basic public interface

What objects will we need to start?

DataMapper

Result – Individual row object

Start with DataMapper

Define basic public interface

What table are we working with? All finders generate SQL They can use “findBySql” internally get() needs a primary key field defined findFirst() can use find() with a LIMIT clause save() can use insert() or update() internally insert() and update() both need fields/values Which fields exist in the table?

What table are we working with?

All finders generate SQL

They can use “findBySql” internally

get() needs a primary key field defined

findFirst() can use find() with a LIMIT clause

save() can use insert() or update() internally

insert() and update() both need fields/values

Which fields exist in the table?

Required fields Built-in validation? How do we handle errors? Field types Cast to specified type or validate automatically? Table relations How do we handle table relations? Loading an external mapper – how?

Required fields

Built-in validation?

How do we handle errors?

Field types

Cast to specified type or validate automatically?

Table relations

How do we handle table relations?

Loading an external mapper – how?

Finders must return FALSE or iterate Results must be able to be in foreach() loop Relations accessible by set field alias Implementation defined ‘contacts’ $user->contacts should have the related fields Relations must also return FALSE or iterate as well as be able to be count()-ed

Finders must return FALSE or iterate

Results must be able to be in foreach() loop

Relations accessible by set field alias

Implementation defined ‘contacts’

$user->contacts should have the related fields

Relations must also return FALSE or iterate as well as be able to be count()-ed

Eager Loading Always loads relations with row Lazy Loading Loads relations only when asked

Wait… How? $user->contacts can’t be an array $user object does not know about mapper Can’t pull in relations dynamically from mapper with “__get” magic method Are we stuck with eager loading?

Wait… How?

$user->contacts can’t be an array

$user object does not know about mapper

Can’t pull in relations dynamically from mapper with “__get” magic method

Are we stuck with eager loading?

Relation Object as a placeholder empty until called Relation Object uses SPL interfaces IteratorAggregate, Countable foreach() – can iterate count($user->contacts) will work Use SPL functions to fetch results upon request

Relation Object as a placeholder empty until called

Relation Object uses SPL interfaces

IteratorAggregate, Countable

foreach() – can iterate

count($user->contacts) will work

Use SPL functions to fetch results upon request

$user->contacts foreach() calls ‘getIterator()’ (IteratorAggregate) Calls findAllRelation(), returns ResultSet object count() calls ‘count()’ (Countable) Calls findAllRelation(), returns count of found rows findAllRelation() calls findAll(), caches result findAll() gets related rows from related mapper with given foreign keys as conditions

$user->contacts

foreach() calls ‘getIterator()’ (IteratorAggregate)

Calls findAllRelation(), returns ResultSet object

count() calls ‘count()’ (Countable)

Calls findAllRelation(), returns count of found rows

findAllRelation() calls findAll(), caches result

findAll() gets related rows from related mapper with given foreign keys as conditions

Adapters Adapter Interface One Initial adapter to test with Adapter_PDO_MySQL Relations Relation Interface Relation_HasMany

Adapters

Adapter Interface

One Initial adapter to test with

Adapter_PDO_MySQL

Relations

Relation Interface

Relation_HasMany

PHPDataMapper _Database _Adapter _PDO _Mysql _Exception _Model _Relation _HasMany _ResultSet _Result

PHPDataMapper

_Database

_Adapter

_PDO

_Mysql

_Exception

_Model

_Relation

_HasMany

_ResultSet

_Result

Why not a generic ‘stdClass’ or an array? A Result object lets us: Keep track of changed fields for update() Use object syntax – $row->name; Suppress undefined property errors with __get() Use array syntax – $row[‘name’]; SPL ArrayAccess interface Suppress undefined index errors with offsetGet() Use getter functions - $row->getName(); Automatic functions for all fields with __call()

Why not a generic ‘stdClass’ or an array?

A Result object lets us:

Keep track of changed fields for update()

Use object syntax – $row->name;

Suppress undefined property errors with __get()

Use array syntax – $row[‘name’];

SPL ArrayAccess interface

Suppress undefined index errors with offsetGet()

Use getter functions - $row->getName();

Automatic functions for all fields with __call()

Simple syntax to get almost any record All results returned are “live” objects Can be altered and saved at any time No writing SQL code for mundane operations Promotes good programming style Easier to always use mapper object than write SQL queries all over the place

Simple syntax to get almost any record

All results returned are “live” objects

Can be altered and saved at any time

No writing SQL code for mundane operations

Promotes good programming style

Easier to always use mapper object than write SQL queries all over the place

Project Page on my blog www.vancelucas.com/phpdatamapper Open-Source Project MIT License On Google Code Martin Fowler’s “P of EAA” http://martinfowler.com/eaaCatalog/

Project Page on my blog

www.vancelucas.com/phpdatamapper

Open-Source Project

MIT License

On Google Code

Martin Fowler’s “P of EAA”

http://martinfowler.com/eaaCatalog/

Vance Lucas, 23 Blog: www.vancelucas.com Email: [email_address] Making websites since age 12 Started learning PHP when PHP3 was new Oklahoma Baptist University – Shawee Bachelor of Business Administration Currently work at Back40Design, Inc. www.back40design.com

Vance Lucas, 23

Blog: www.vancelucas.com

Email: [email_address]

Making websites since age 12

Started learning PHP when PHP3 was new

Oklahoma Baptist University – Shawee

Bachelor of Business Administration

Currently work at Back40Design, Inc.

www.back40design.com