This is the PHPeas Specification document version 1.0. It describes the standards and patterns that make up PHPeas.

The PHPeas home page is: http://phpeas.sourceforge.net

Send all questions, comments, etc. to phpeas@gmail.com

Table of Contents

  1. Introduction
  2. Fundamentals
    1. What is a Pea?
    2. Properties and Methods
  3. Properties
    1. Overview
    2. Accessor Methods
  4. Introspection
    1. Overview
    2. Overview of PHPeas Design Patterns
    3. Design Patterns for Constructors
    4. Design Patterns for Properties
      1. Simple Properties
      2. Boolean Properties
    5. Security
  5. Appendix I: GNU Free Documentation License

Introduction

The goal of PHPeas is to define a common software component model for PHP, so that standard APIs can be developed that can be manipulated programmatically across different systems and platforms.

Throughout this document the words "PHPea" or "pea" are used as interchangable nouns to describe any PHP object which conforms to the PHPeas Specification (i.e. this document).

Fundamentals

What is a Pea?

A PHPea is an object oriented, reusable software component built using the PHP 5 Object Model.

The primary, unifying feature that distinguishes a PHPea is its support for instrospection, specifically by following the design patterns in this specification document.

A pea is not required to inherit from any particular base class or interface.

Properties and methods

The two most important features of a PHPea are the set of properties it exposes and the set of methods it allows other components to call.

Basically, properties are named attributes associated with a pea that can be read or written by calling appropriate methods (accessors) on the pea.

The methods a PHPea exports are just normal PHP class methods which can be called from other components.

Properties

Overview

Properties are discrete, named attributes of a PHPea that can affect its appearance or behavior. Properties can also have any arbitrary type such as the standard PHP primitive data types (boolean, integer, etc.) and builtin or user-defined class or interface types (SoapClient, MyClass, etc.)

Properties can be accessed programatically by other components calling their accessor methods (also known as getters and setters). See below for more information.

Accessor Methods

Properties are always accessed via method calls on their owning object. For readable properties, there will be a getter method to read the value of the proeprty. For writable properties, there will be a setter method to update the value of the property.

Properties do not necessarily need to be simple data fields, they can be computed values, perform validation, etc.

See the Design Patterns For Properties section below for more information about naming accessor methods.

Introspection

Overview

In order to be able to dynamically discover what properties and methods a PHPea supports at runtime, a process called introspection is used. Introspection is a combination of the PHP Reflection API and simple design patterns.

Reflection is used to gather information about the methods supported by a target pea, then some design patterns are applied to figure out from those methods what properties and public methods are supported.

The PHPeas_PeaUtils class provided with the PHPeas specification already understands the design patterns and conventions of PHPeas. This class provides a uniform way to introspect on different peas.

Overview of PHPeas Design Patterns

By the term design patterns we mean conventional names and signatures for sets of methods and/or interfaces that are used for standard purposes. For example the use of getFoo() and setFoo() methods to retrieve and set the values of a property named: "foo".

These design patterns have two uses. First they are a useful documentation hint for developers. By quickly identifying particular methods as fitting standard design patterns, developers can more quickly assimilate and use new classes. Secondly, we can write tools and libraries that recognize design patterns and use them to analyze and understand components. In particular for PHPeas we use automatic identification of design patterns as a way for tools to identify properties and public methods.

Design Patterns for Constructors

PHPeas must declare a public, default, no argument constructor. This is nescessary for some of the reflection operations that are performed on a pea.

It is acceptable to have arguments declared in the constructor, as long as they are all declared with default values, and no exceptions will be thrown if the no argument version of the constructor is invoked.

Design Patterns for Properties

Simple Properties

By default, we use design patterns to locate properties by looking for methods of the form:

public function get<PropertyName>(); public function set<PropertyName>( $valueIn );

If we discover a matching pair of "get<PropertyName>()" and "set<PropertyName>()" methods, then we regard these methods as defining a read-write property whose name will be "<propertyName>". We will use the "get<PropertyName>()" method to get the property value and the "set<PropertyName>()" method to set the property value. The pair of methods may be located either in the same class or one may be in a base class and the other may be in a derived class.

If we find only one of these methods, then we regard it as defining either a read-only or a write-only property called "<propertyName>"

Properties are expected to be named in Java style "camelCase". That is, the first character of the property should be lower case, a through z, with only the first letter of each "word" in the property name capitalized, and all "words" directly next to each other, with no other characters between "words". Some example property names include: $foo, $memberId, $webServiceUrl, $employeeName, $z, $url, etc. Do not prefix private or protected properties with an underscore character ("_").

In the case of acronyms, the first letter should be uppercase, with the rest lowercase.

So a simple read-write property "foo" might be represented by a pair of methods:

public function getFoo(); public function setFoo( $valueIn );

Boolean Properties

In addition, for boolean properties we allow a getter method to match the pattern:

public function is<PropertyName>();

This "is<PropertyName>()" method may be provided instead of a "get<PropertyName>()" method, or it may be provided in addition to a "get<PropertyName>()" method.

In either case, if the "is<PropertyName>()" method is present for a boolean property then we will use the "is<PropertyName>()" method to read the property value in preference to the "get<PropertyName>()" method.

An example boolean property might be:

public function isBar(); public function setBar( $valueIn );

Security

The high-level Introspection APIs only provide information on "public" methods of target peas.

Appendix I: GNU Free Documentation License

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We have designed this License in order to use it for manuals for free software, because free software needs free documentation: a free program should come with manuals providing the same freedoms that the software does. But this License is not limited to software manuals; it can be used for any textual work, regardless of subject matter or whether it is published as a printed book. We recommend this License principally for works whose purpose is instruction or reference. 1. APPLICABILITY AND DEFINITIONS This License applies to any manual or other work, in any medium, that contains a notice placed by the copyright holder saying it can be distributed under the terms of this License. Such a notice grants a world-wide, royalty-free license, unlimited in duration, to use that work under the conditions stated herein. The "Document", below, refers to any such manual or work. Any member of the public is a licensee, and is addressed as "you". 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