Propel Your PHP Applications

Hans LellelidInternational PHP Conference

2007-11-06

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Introduction• My name is Hans Lellelid• Developer + manager at Applied Security,

Inc. (near Washington DC).• I wrote/ported original Propel.• I currently manage the project with David

Zülke – and an ever-growing team of developers.

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This Talk• Overview of Propel• A typical work cycle• More in-depth usage• Advanced features• Slides available at

http://propel.phpdb.org/presentations/

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Pre-Flight CheckGoing over the basics.

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Fact Sheet• Propel is an ORM tool for PHP5.

– It is also a code (and DDL) generator.

• Based on Apache Torque.• Includes runtime and generator

frameworks.• Uses PDO (v1.2 uses Creole)• Generator uses Phing tasks to create the

PHP and SQL files.• Installs using PEAR installer.

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ORM Patterns in PHP• The most common alternative ORM pattern

in PHP is ActiveRecord.– (Thank you, Ruby on Rails!)

• Propel is not an ActiveRecord implementation: it is a Row Data Gateway + Table Data Gateway implementation.

• Key differences:– Clean division of labor between table

operation objects and row instances.– RDG and TDG are inherently simpler, more

transparent, models.

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Motivations & Purpose• Created because nothing comparable

existed for PHP at the time.• Designed to facilitate prototyping and RAD• Basic Philosophy: Database tasks should

feel as simple as they actually are.• Designed for “enterprise” frameworks.

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Requirements• PHP 5

– Version 1.3 requires PHP >= 5.2– SPL, PDO (1.3), XML, XSLT

• Phing• A supported database. Currently Propel

supports: MySQL, PostgreSQL, MSSQL, Oracle, SQLite

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Propel will ...• Generate classes to represent your

database (model) in an OOP way.– “Object” classes for rows (RDG)– “Peer” classes for table operations (TDG)

• Build SQL (DDL) to initialize your database.• Use unit-of-work pattern to wrap nested

inserts in transactions.• Provide Exception-based error handling.• Allow you to avoid SQL (if you want).• Type-cast output and escape input.

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But Propel won't ...• Build forms, reports, or other display stuff.

– Several full frameworks are built around Propel to provide this (e.g Symfony, Agavi)

• Help you design your database.• Prevent you from writing insecure code.• Replenish essential electrolytes after a hard

workout.

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Flight PlanA Typical Propel Work Cycle

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A Typical Workflow• Design Database in XML (schema.xml)• Configure generator (build.properties)• Configure runtime (runtime-conf.xml)• Build SQL DDL and PHP classes.• (Maybe) initialize database.• Use newly-built objects in your application.

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schema.xml

<?xml version="1.0"?><database name="demo">

<table name="session"><column name="id" type="integer" primaryKey="true" /><column name="name" type="varchar" size="255" /><column name="room" type="varchar" size="16" /><column name="speaker" type="varchar" size="32" />

</table></database>

• The schema.xml is the single authority for your data model.

• Written in [quite intuitive] XML

• Will be validated by build process (DTD and schema provided).

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build.properties• Generator uses “properties” files (Phing)• Propel needs to know (at least) your

RDBMS and project name.• It's often simplest to start with the

provided “bookstore” example.• Example minimal build.properties:

propel.project = myprojpropel.database = mysqlpropel.database.url = mysql:dbname=test

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runtime-conf.xml• Runtime config expressed in XML.• Configures connection and (optionally)

PEAR logging facility.• Gets converted to PHP by build process.

<config><propel>

<datasources default="myproj"><datasource id="myproj">

<adapter>mysql</adapter><connection>

<dsn>mysql:dbname=test</dsn></connection>

</datasource></datasources>

</propel></config>

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Build!• Run propel-gen /path/to/projdir to

build the SQL DDL and PHP classes.• Watch output for errors. (They're red.)

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Initialize DB• Use propel-gen /path/to/projdir

insert-sql to run the generated DDL statements against your configured database.

• This will delete any existing data!

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Start using new OM• Initialize Propel

require_once 'propel/Propel.php';Propel::init('/path/to/myproj-conf.php');

• Configure your include_path to include the output directory.– Propel 1.3 uses SPL autoload.

• Begin reading and writing DB rows with your new object model.

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Cruising AltitudeGetting comfortable with Propel.

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Column Types• Propel uses an abstract subset of SQL

types.• SQL types are mapped to specific PHP

types.• You can override the SQL type for a

column.• Temporal values (DATE, TIME, TIMESTAMP)

will use PHP DateTime objects.

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Expressing Relationships• Relationships between tables are defined

using foreign keys.– Even for systems that don't support true FK

constraints.

• Propel supports single or composite foreign keys.

• Support for deletion cascading emulation.• The related objects can be get/set just like

simple column values.

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Selecting Rows• retrieveByPK() static method exists to

select a single row.• Criteria provides an OO approach to

building queries.• Smart handling of column types.• Multiple “Criterion” objects can be grouped

together to form complex queries.• You can also use SQL, if you prefer.

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Customization• Build properties customize code generation.• Override method and constant naming from

the schema.xml• Empty stub object & peer classes for

custom methods:– New methods or– Override parent (base) methods

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Over-DriveWait ... I thought we were using

airplane metaphors.

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Locator Objects (LOBs)• LOB columns returned as PHP streams.

– This is the PDO design (though there are some exceptions).

• Mutator methods support streams or (string) file contents.

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Inheritance• Propel supports table-per-class-hierarchy

inheritance.• Subclasses can be enumerated in the

schema.xml (faster) or resolved at runtime (more flexible).

• Plans in place for other inheritance models.

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Other Features• Reverse engineer existing databases

(requires Creole)• Import and export data as XML• Generate Graphviz ERD from schema.xml• Represent trees in SQL using nested set

approach.

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Extension Paths• Integrating with other Phing projects• Custom platform classes

– Affects generation of SQL DDL

• Custom builder classes– Determine how your classes are built.

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The 2.0 Horizon• Criteria redesign• New inheritance models• Eagerly awaiting PHP6 (or 5.3)

– Namespaces– Late static binding

• Plugin-based builder framework.

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On Behalf of the Flight Crew ...

Thanks for listening. :)