PHP and MySQL Web Development 4th Ed-tqw-_darksiderg

160 Chapter 6 Object-Oriented PHP
Understanding Object-Oriented Concepts
Modern programming languages usually support or even require an object-oriented
approach to software development. Object-oriented development attempts to use the
classifications, relationships, and properties of the objects in the system to aid in program
development and code reuse.
Classes and Objects
In the context of OO software, an object can be almost any item or concept—a physical
object such as a desk or a customer; or a conceptual object that exists only in software,
such as a text input area or a file. Generally, you will be most interested in objects,
including both real-world objects and conceptual objects, that need to be represented in
software.
Object-oriented software is designed and built as a set of self-contained objects with
both attributes and operations that interact to meet your needs. Attributes are properties
or variables that relate to the object. Operations are methods, actions, or functions that the
object can perform to modify itself or perform for some external effect. (You will hear
the term attribute used interchangeably with the terms member variable and property, and
the term operation used interchangeably with method.)
Object-oriented software’s central advantage is its capability to support and encourage
encapsulation—also known as data hiding. Essentially, access to the data within an object is
available only via the object’s operations, known as the interface of the object.
An object’s functionality is bound to the data it uses.You can easily alter the details
controlling how the object is implemented to improve performance, add new features, or
fix bugs without having to change the interface. Changing the interface could have ripple
effects throughout the project, but encapsulation allows you to make changes and fix
bugs without your actions cascading to other parts of the project.
In other areas of software development, object orientation is the norm, and
procedural or function-oriented software is considered old fashioned. However, most
web scripts are still designed and written using an ad hoc approach following a functionoriented
methodology.
A number of reasons for using this approach exist. Many web projects are relatively
small and straightforward.You can get away with picking up a saw and building a wooden
spice rack without planning your approach, and you can successfully complete the
majority of web software projects in the same way because of their small size. However,
if you picked up a saw and attempted to build a house without formal planning, you
wouldn’t get quality results, if you got results at all.The same is true for large software
projects.
Many web projects evolve from a set of hyperlinked pages to a complex application.
Complex applications, whether presented via dialog boxes and windows or via dynamically
generated HTML pages, need a properly thought-out development methodology.