Professional LAMP: Linux®, Apache, MySQL®, and PHP5 Web Development

1.1. Object-Oriented Changes

The changes that follow relate to the OOP model and associated features and related topics. The majority of these changes are covered in greater detail in Chapter 2, but are also briefly outlined here for your quick reference.

1.1.1. Passing Objects

One big impact of OOP changes in PHP5 is the way that variables are passed as parameters to functions. In PHP4, by default, variables were passed by value instead of by reference, unless denoted otherwise with the syntax &$varname. In PHP5, the default is to assign a value by reference.

1.1.2. Exceptions

In a nutshell, exceptions are the procedures that happen when something goes wrong. Instead of your program completely halting when it reaches an unexpected error, you can now exert a little more control over what the program should do when it reaches said error. You are probably familiar with the set_error_handler() function available in PHP4. If you aren't, the purpose of this function is to define a user function for error handling. However, it had many limitations in its implementation. For example, it would not work if the error was type E_ERROR, E_PARSE, E_CORE_ERROR, E_CORE_WARNING, E_COMPILE_ERROR, E_COMPILE_WARNING, and most of E_STRICT. Also, if the error occurred before the set_error_handler() function script, the function would never be called. With PHP5 comes a new framework for handling exceptions.

1.1.2.1. Try/Catch/Throw

If you have previous programming experience with languages like ...