Blog

PHP Classes and Objects Examples
Posted on March 22, 2018 in PHP by Matt Jennings

Class Example, Object, and Access Modifiers (Public, Private, Protected) Examples

/*
public - the property or method can be accessed from everywhere. This is default
protected - the property or method can be accessed within the class and by classes derived from that class
private - the property or method can ONLY be accessed within the class
*/
class Person
{
  const AVG_LIFE_SPAN = 79;
 
  public $firstName;
  public $lastName;
  public $yearBorn;
 
  // Constructor function that is called
  // whenever an object is instantiated
  // from the class
  function __construct()
  {
    $this->firstName = 'Samuel Longhorne';
    $this->lastName = 'Clemens';
    $this->yearBorn = 1899;
  }
  public function getFirstName()
  {
    return $this->firstName . ' ' . $this->getLastName();
  }
 
  private function getLastName()
  {
    return $this->lastName ;
  }

  protected function kewlPerson() 
  {
    return getFirstName() . ' is a kewl person!';
  }

  static public function blah1() 
  {
    return 'blah1';
  }

  static protected function blah2() 
  {
    return 'blah2';
  }

 }

class DeadPerson extends Person {
  public function getDeadPersonInfo() {
    // Grabbed $this->firstName and other variables
    // from Person class because they're inherited
    return $this->firstName . ' ' . $this->lastName . ', ' . $this->yearBorn . ' is now dead!';
  }
}

class OtherPerson {
  public $randomPersonName;

  public function __construct($randomPersonName) {
    $this->randomPersonName = $randomPersonName . ': ' . Person::blah1();
  }

  public function getRandomPerson() {
    return $this->randomPersonName;
  }

  public function protectedTest() {
    return Person::blah2();
  }
}
 
// Class instantiation or object creation 
$personObj = new Person();

/*
Public method output, 
including the private method function call inside the
public method: 
'Samuel Longhorne Clemens'
*/
echo '$personObj: ' . $personObj->getFirstName() . PHP_EOL;

// Class instantiation or object creation 
// on inherited object
$deadPersonObj = new DeadPerson();

// Inherited class method call
echo '$deadPersonObj: ' . $deadPersonObj->getDeadPersonInfo() . PHP_EOL;


// Another class instantiation, or object creation
// and Person::blah1() is echo out at the end because it's
// accessing a static class and using the double colon operator
$otherPersonObject = new OtherPerson('Billie');
echo $otherPersonObject->getRandomPerson() . PHP_EOL;

/*
Method call below doesn't work because Person::blah2()
method was a static class
*/
echo $otherPersonObject->blah2();

 Access Modifiers

<?php
/*
public - the property or method can be accessed from everywhere. This is default
protected - the property or method can be accessed within the class and by classes derived from that class
private - the property or method can ONLY be accessed within the class
*/

class Fruit {
  public $name;
  public $color;
  public $weight;

  function set_name($n) {  // a public function (default)
    $this->name = $n;
  }
  protected function set_color($n) { // a protected function
    $this->color = $n;
  }
  private function set_weight($n) { // a private function
    $this->weight = $n;
  }
}

$mango = new Fruit();
$mango->set_name('Mango'); // OK
$mango->set_color('Yellow'); // ERROR
$mango->set_weight('300'); // ERROR
?>