2. PHP Class Inheritance

//need to include parent class to define the parent class
include "contact_info.php";
 
//To inherit from a class, simply add extends <class name>
 
/* a child class would automatically inherits all the class variables &
   class functions defined in the parent class. Therefore, business_contact_info has
   all the class variables & functions in the parent class contact_info   */
class business_contact_info extends contact_info
{
	//additional class variables only in this class
	var $company;
	var $title;
 
	/*Ovewriting the constructor function 
	To set a title for when creating a new business_contact
	*/
	public function business_contact_info($name, $title)
	{
		/* name is pass along over to the parent class contact_class
		then the title is set in the business_contact_info class. 
 
		To call a parent class's function, just use:
		[Parent ClassName]::[Parent class Function Name] (whatever parameter)
		*/
 
		contact_info::contact_info($name);
 
		$this->title = $title;
	}
 
	public function set_company($company)
	{
		$this->company = $company;
	}
 
	/* To prevent a child class from overwriting a parent class's function
	simply put "final" in the parent's function definition
	For example: to prevent overwrite of function print_contact_info()
	in parent class contact_info. define the function in parent class contact_info as:
	final function print_contact_info() ...
	*/
 
	/* overwriting a function */
	/* in PHP, to overwrite a function that is defined in parent class. 
	simply define a function with the same name in the child class. */	
	public function print_contact_info()
	{
		$output = "Name is: ".  $this->name ."<BR>". 
			       "Phone Number is: ". $this->phone_number. "<BR>". 
				   "Company name: ".$this->company. "<BR>".
				   "Title: ".$this->title. "<BR>".
				   "Note: ".$this->note;
 
		return $output;
	}
 
} //end of class

class contact_info
{
  /* declare some class properties as variables */
  var $name;
  var $phone_number;
  var $note;
 
  /* Constructor is simply a function with same name as the class */
  public function contact_info($name)
  {
	$this->name = $name;
  }
 
  /* To assign a value to the class variable - use $this->
 */
  /* NOTE: the variablename when use in $this->, does NOT use the $ in front of variable name */
  public function set_phone_number($phone_number)
  {
	$this->phone_number = $phone_number;
  }
 
  public function set_note($note)
  {
	$this->note = $note;
  }
 
  /* function print out the contact detail information by appending the value of class variables */
  public function print_contact_info()
  {
	$output = "Name is: ".  $this->name ."
". "Phone Number is: ". $this->phone_number. "
". "Note: ".$this->note;
	return $output;
  }
} //end of class

include "business_contact_info.php";
 
$my_biz_contact = new business_contact_info("Jason", "Software Engineer");
$my_biz_contact->set_phone_number("888-999-1111");
$my_biz_contact->set_note("Jason is a great coder and designer.");
$my_biz_contact->set_company("MonkeyCanCode.com");
 
echo $my_biz_contact->print_contact_info();