PHPeas Specification 1.0

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.

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PHPeas Specification 1.0

Table of Contents

Introduction

Fundamentals

What is a Pea?

Properties and methods

Properties

Overview

Accessor Methods

Introspection

Overview

Overview of PHPeas Design Patterns

Design Patterns for Constructors

Design Patterns for Properties

Simple Properties

Boolean Properties

Security

Appendix I: GNU Free Documentation License