Classes

• A class declaration in PHP defines the properties and behavior of any objects of the class existing within the application. A class is like a blueprint, describing the data and functions that objects of the class will exhibit. For example, if a class declares a data variable, each object of the class will contain a copy of that variable. Class declarations typically define both data and functions. The collected properties and behavior within a class are all included to help objects of the class carry out a well-defined set of application responsibilities.
  
  

Objects

• When a PHP project, such as a website or Web application, creates class declarations, other PHP scripts are able to create objects of the classes indicated. The PHP language provides a number of classes as standard, which PHP scripts can also instantiate, as well as optionally including custom classes. The following sample code demonstrates creating an object of a class, storing a reference to the object in a variable:
  
  $my_object = new Lovely_Helper;
  
  When this code executes, the server will execute the code listed within the constructor function in the "Lovely_Helper" class declaration, returning an object with the data and functions listed in that declaration.
  
  

Constructor Function

• The constructor function executes when an object of a class is created by "customer" code. "Customer" code is the code in any script or application area that is external to the class declaration, but that can access the functionality the class is aiming to provide. The constructor function can optionally take parameters. The following example code demonstrates the outline of a constructor function for the "Lovely_Helper" class:
  
  function Lovely_Helper(){
  
  //constructor code here
  
  }
  
  Inside the constructor function, the class can carry out any processing necessary to instantiate objects of the class.
  
  

Properties

• In most cases, a class constructor will assign values to certain class variables. Sometimes, these values may be passed as parameters when external code creates an object of the class using the "new" keyword. The following extended code sample demonstrates the inclusion of a class variable:
  
  var $my_name;
  
  function Lovely_Helper($name = "Jim") {
  
  this->$my_name = $name;
  
  }
  
  The code provides a default value for the variable in case "customer" code does not pass any parameters. Once the constructor method for this class has executed, the "my_name" variable will have a value, either the one passed by "customer" code or the default value provided within the constructor code.