week11.md

footer:@johnsonch :: Chris Johnson :: Web Development with PHP and MySQL :: Week 11 autoscale: true

#Web Development with PHP and MySQL ##Object Oriented PHP ###Week 11

##What is inheritance?

• Inheritance is a mechanism of extending an existing class.
• By inheriting a class, we create a new class with all the functionality of an existing class, plus we can add new properties and methods to the new class.

---

##What is inheritance?

class Person{
  private $first_name;
  private $last_name;
  function __construct($first, $last){
    $this->$first_name = $first;
    $this->$last_name = $last;
  }

  public function getFirstName(){
    $this->first_name;
  }
  public function getLastName(){
    $this->last_name;
  }

}

class Teacher extends Person{
  public function salary(){
    return 0;
  }
}

class Student extends Person{
  public function gpa(){
    return 4.0;
  }
}

$student = new Student('Bart', 'Simpson');
$teacher = new Teacher('Homer', 'Simpson');

echo $teacher->getFirstName; // Homer
echo $student->getFirstName; // Bart
echo $student->salary(); // KABOOOOOOOMMMM
echo $student->gpa(); // 4.0

---

##How do you overrride properties or methods?

• Create a member in a subclass with the same name as it has in the parent class.

---

##How do you overrride properties or methods?

class Person{
  private $first_name;
  private $last_name;
  function __construct($first, $last){
    $this->$first_name = $first;
    $this->$last_name = $last;
  }

  public function fullName(){
    echo "$this->$first_name $this->$last_name";
  }
}

class Teacher extends Person{
...
  public function fullName(){
    echo "$this->$title $this->$last_name";
  }
  
}

class Student extends Person{
...
}

$student = new Student('Bart', 'Simpson');
$teacher = new Teacher('Homer', 'Simpson');
$teacher->$title = 'Mr.';

echo $student->fullName(); // Bart Simpson
echo $teacher->fullName(); // Mr. Simpson