Object Oriented Programming With PHP 4.1.x

Object Oriented Programming provides raw power to PHP 4.1.x

Part 1:Introduction
First off, an object (also know as a class) is a very simple section ofcode that has a section of its own variables and functions. In a simpleway an object is kind of like a program itself.
Objects can be used for many different things as they are veryexpandable. What an object is capable of doing is entirely up to thedeveloper. A class can be used for things as simple as creating a linkand or to store data loaded from a file and or SQL query.

Part 2: Basic Syntax
The basic syntax of an object is quitesimple. As you can see in the example bellow the syntax is muchdifferent from that of a function.

Class className{<? code ?>}

In the above code I have created a simple object that is named "className".

Part 3: Object Variables
An Object can have variablesdeclared inside the object. While it is not necessary for an object tohave any variables it is most likely that they will. Most, if not all,objects use variables to store information that can be accessed at anytime by any function within ,and outside of, the object. To create anobject variable you must use the 'var' command when creating thevariable. An example of variable declaration is listed bellow.

Class className{var $variable1; var $variable2; <? code ?>}

Part 4: Accessing Object Variables
The method of accessingobject variables is different depending on if you are accessing thevariables from within or outside of the object.

- Accessing From Within The Object:
To access a variable from within an objects own function you must use the '$this' reference. An example of this would be:

$localvar = $this->variable1;

Notice how we didn't not use the '.' (period) operator but instead weused the '->' (reference/arrow) operator. This is because we arepointing to the variable within the object.

- Accessing From Outside of The Object:
Accessing a variable from out side of an object isn't that dissimilarfrom accessing one within the object. Instead of using the '$this'reference you use the name of the object you wish to access. An exampleof this would be:

	$localvar = $object->variable1;

Part 5: Object Functions
Creating an object function is not that dissimilar from creating anormal function. To create an object function all you have to do iscreate a function inside of the objects brackets as shown bellow.

Class className{ var $variable1; var $variable2; function classFunction($arg1, $arg2)  { <? function code ?> }}

In the above code I have create a function called classFunction. Thisfunction can not be called from out side of object unless you use apointer reference. We will talk more about that later on. Also, afunction can have any amount of arguments that will. I have used twoarguments above called $arg1 and $arg2.

Part 6: Object Constructors
Although not required it is good practice for each object to have aconstructor. A constructor is a function within the object that iscalled when the object is created. A constructor is mostly used forsetting default and or initiating values for the objects variables.

Class className{ var $variable1; var $variable2; function className($arg1, $arg2="default value") { $this->variable1 = $arg1; $this->variable2 = $arg2; } function classFunction($arg1, $arg2) { <? function code ?> }}

As you can see above I have given $arg2 in the constructor function adefault value. This is what the value of $arg2 will be if the user doesnot pass any value to $arg2.

Part 7: Using The Object
Using an object is quite simple.First We must create the object. This is done by setting a variableusing the new command as shown bellow:

$object_var = new className("test");

Notice how I passed a value when creating the object. This is donebecause it is required by the object's constructor function. If both ofthe object's constructor function's arguments have a default value thenthis would not be required.
Using an objects functions is also quite simple. To do this wewill once again be using the '->' (reference/arrow) operator asshown bellow:

$object_var->classFunction("value1", "value2");

If the function returns a variable then you would use the function as follows:

$return_val =  $object_var->classFunction("value1", "value2");

Part 8: ConclusionObjects can be a great tool for any developerbut try not to over use them. From my experience objects are best usedfor storing multiple pieces of information and or for easy to use,automated, tasks such as creating html/xml style tags.
Remember, objects to take up more memory then standard functions andvariables so if you can accomplish the same task without using anobject I recommend you do so.

Object Oriented Programming With PHP 4.1.x
Object Oriented Programming provides raw power to PHP 4.1.x Part 1:Introduction First off, an object (also know as a class) is a very simple section of code that has a section of its own variables and functions. In a simple way an object is kind of like a program itself. Objects can be used fo...
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