Star A Beginner's Crash Course into Object Oriented Programming
Linked by John Collins on Wed 21st Apr 2004 06:42 UTC
General Development The purpose of this article is to give a novice programmer the basic idea of what OOP is, as implemented using PHP. Readers should have a basic knowledge of programming ie what variables are, variable types, basic methods of writing comments, and how to enter code into a text editor.
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PHP4 Object orientation
by Bryan Feeney on Wed 21st Apr 2004 10:08 UTC

It's also important to realise that PHP4 uses value-semantics (as opposed to the more usual reference semantics) for objects. Thus if you say

$bill = new Student("Bill", "Male");
$william = $bill;

three objects will be created. The new command creates an object, and then a copy of this is placed in the variable $bill. On the second line another object is created (a copy of the one in $bill) and is placed in $william.

Thus for the following

$bill = new Student("Bill", "Male");
$william = $bill;
$bill->name = "Bill Gates";
echo $bill->name . "n";
echo $william->name . "n";

You would get


Bill Gates
Bill


This becomes even more of an issue in functions. As a result most PHP programmers explicity pass by reference.

The following code passes by reference

$bill =& new Student("Bill", "Male");
$william =& $bill;
$bill->name = "Bill Gates";
echo $bill->name . "n";
echo $william->name . "n";


and the output is

Bill Gates
Bill Gates


In PHP5 objects will use reference semantics only, and there will be no need for hundreds of & symbols in your code.