OOP: Object Oriented Programs

Objects are a data structure that has both properties (data) and methods (functions). We create a Class, the definition of the object, and then we can create instances of the class (variables).

We can use OOP notation very easily without actually creating a Class. For instance we could say

$ny->capital="Albany";
$ny->name="New York";

We have created an instance of an object called $ny that has two properties or pieces of data, the name and the capital. We can use this instance variable the same way that we would any pother variable:

if($ny->capital=="New York") ...

We can also create instances that are elements of an array:

$state['NY']->name="New York";
$state['NY']->capital="Albany";

Although we have created an instance of the generic object, we have not actually created a class. The code below will create a new class called State:

class State {
  var $name;
  var $capital;
  function setValue($name,$capital) {
    $this->name=$name;
    $this->capital=$capital;
  } //setValue
  function information() {
    return 'The capital of '.$this->name.' is '.$this->capital.'.';
  } //information
} //State

We can then declare a variable as a new State and use the two methods setValue and information as show below:

 $ny = new State();
 $ny->setValue("New York","Albany");
 echo $ny->information();