Classess & Objects¶

Creating a Classess¶

<?php
class Person
{
}

Creating an Object¶

<?php
class Person
{
}
$myObject = new Person();
?>

Create Properties¶

<?php
class Person
{
    public $firstName = "Samel";
    public $lastName = "Clemens";
    public $yearBorn = "1988";
}
$myObject = new Person();
?>

Accessing Properties¶

<?php
class Person
{
    public $firstName = "Samel";
    public $lastName = "Clemens";
    public $yearBorn = "1988";
}
$myObject = new Person();
echo $myObject->firstName."<br>";
$myObject->firstName = "S.L";
echo $myObject->firstName;
//output:
//Samel
//S.L
?>

Note

we don’t use $ to access the properties values

Creating Constans¶

<?php
class Person
{
    const AVG_LIFE_SPAN = 79;
    public $firstName = "Samel";
    public $lastName = "Clemens";
    public $yearBorn = "1988";
}
$myObject = new Person();
echo $myObject::AVG_LIFE_SPAN."<br>";
echo Person::AVG_LIFE_SPAN;
//output
//79
//79
?>

Note

we can access constant value by using the object of the class or the class itself

Creating Methods¶

<?php
 class Person
{
    const AVG_LIFE_SPAN = 79;
    public $firstName;
    public $lastNamens;
    public $yearBorn;

    function __construct()
    {
        echo "I'm in the constructor";
        $this->firstName = "Samel";
        $this->lastName = "Clemens";
        $this->yearBorn = "1988";
    }

    public function getFirstName()
    {
        return $this->firstName;
    }
    public function setFirstName($tempName)
    {
        $this->firstName = $tempName;
    }
}
$myObject = new Person();
echo $myObject->getFirstName()."<br>";
echo $myObject->getFirstName()."<br>";
$myObject->setFirstName("Sam");
echo $myObject->getFirstName();
//I'm in the constructorSamel
//Samel
//Sam
?>

Note

A constructor will execute when creating a new object
A conststructor is created by using function __construct(){}

Initial Parameters¶

<?php

 class Person
{
    const AVG_LIFE_SPAN = 79;
    public $firstName;
    public $lastNamens;
    public $yearBorn;
    function __construct($tempFirst = "", $tempLast = "", $tempBorn = "")
    {
        $this->firstName = $tempFirst;
        $this->lastName = $tempLast;
        $this->yearBorn = $tempBorn;
    }
    public function getFirstName()
    {
        return $this->firstName;
    }
    public function setFirstName($tempName)
    {
        $this->firstName = $tempName;
    }
}
$myObject = new Person("Samuel Langhorne", "Clemens", 1899);
echo $myObject->getFirstName();
//output:
//Samuel Langhorne
?>

Note

Initializing parameters of the constructor prevent an error from happinnig if no parameters were givin

Inheritance¶

<?php
 class Person
{
    const AVG_LIFE_SPAN = 79;
    public $firstName;
    public $lastNamens;
    public $yearBorn;
    function __construct($tempFirst = "", $tempLast = "", $tempBorn = "")
    {
        echo "Person Constructor<br>";
        $this->firstName = $tempFirst;
        $this->lastName = $tempLast;
        $this->yearBorn = $tempBorn;
    }
    public function getFirstName()
    {
        return $this->firstName;
    }
    public function setFirstName($tempName)
    {
        $this->firstName = $tempName;
    }
    public function getFullName()
    {
        echo "Person->getFullName()<br>";
        return $this->firstName." ".$this->lastName."<br>";
    }
}
class Author extends Person
{
    public $penName = "Mark Twain";
    public function getPenName()
    {
        return $this->penName."<br>";
    }
    //child methods with same name will overide parents method
    public function getFullName()
    {
        echo "Author->getFullName()<br>";
        //firstName and lastName are parents attriputes that child can access
        return $this->firstName." ".$this->lastName."<br>";
    }
}
//Author will access parent method getFullName()
$newAuthor = new Author("Samuel Langhorne", "Clemns", 1899);
echo $newAuthor->getFullName();
echo $newAuthor->getPenName();
//output
//Person Constructor
//Author->getFullName()
//Samuel Langhorne Clemns
//Mark Twain
?>

Note

If we comment child function getFullName() output will be Person->getFullName()

Public, Protected and private¶

php cocumentation for visibility

<?php
/**
 * Define MyClass
 */
class MyClass
{
    public $public = 'Public';
    protected $protected = 'Protected';
    private $private = 'Private';

    function printHello()
    {
        echo $this->public;
        echo $this->protected;
        echo $this->private;
    }
}

$obj = new MyClass();
echo $obj->public; // Works
echo $obj->protected; // Fatal Error
echo $obj->private; // Fatal Error
$obj->printHello(); // Shows Public, Protected and Private


/**
 * Define MyClass2
 */
class MyClass2 extends MyClass
{
    // We can redeclare the public and protected properties, but not private
    public $public = 'Public2';
    protected $protected = 'Protected2';

    function printHello()
    {
        echo $this->public;
        echo $this->protected;
        echo $this->private;
    }
}

$obj2 = new MyClass2();
echo $obj2->public; // Works
echo $obj2->protected; // Fatal Error
echo $obj2->private; // Undefined
$obj2->printHello(); // Shows Public2, Protected2, Undefined

?>

Note

public scope to make that variable/function available from anywhere, other classes and instances of the object
protected scope when you want to make your variable/function visible in all classes that extend current class including the parent class
private scope when you want your variable/function to be visible in its own class only

example

<?php
 class Person
{
    const AVG_LIFE_SPAN = 79;
    protected $firstName;
    protected $lastNamens;
    protected $yearBorn;
    function __construct($tempFirst = "", $tempLast = "", $tempBorn = "")
    {
        echo "Person Constructor<br>";
        $this->firstName = $tempFirst;
        $this->lastName = $tempLast;
        $this->yearBorn = $tempBorn;
    }
    protected function getFirstName()
    {
        return $this->firstName;
    }
    protected function setFirstName($tempName)
    {
        $this->firstName = $tempName;
    }
    protected function getFullName()
    {
        echo "Person->getFullName()<br>";
        return $this->firstName." ".$this->lastName."<br>";
    }
}
class Author extends Person
{
    protected $penName = "Mark Twain";
    public function getPenName()
    {
        return $this->penName."<br>";
    }
    public function getFullName()
    {
        echo "Author->getCompleteName()<br>";
        //access protected properties through this public method
        return $this->firstName." ".$this->lastName."a.k.a. ".$this->penName."<br>";
    }
}
$newAuthor = new Author("Samuel Langhorne", "Clemns", 1899);
echo $newAuthor->getFullName();
//output
//Person Constructor
//Author->getCompleteNme()
//Samuel Langhorne Clemnsa.k.a. Mark Twain
?>

Static¶

<?php
class Foo
{
    public static $centuryPopular = "19th";
    public static function getCentury()
    {
        return self::$centuryPopular;
    }
}
echo Foo::$centuryPopular;
echo "<br>";
echo Foo::getCentury();
?>

Note

Use self to access static properties inside a class
Use parent to access properties from an ingerited class

Include and Require¶

<?php
include 'Person.php';
include_once 'Authors.php';
require 'RandomClass.php';
$newAuthor = new Author("sam", "clem", 1889);
echo $newAuthor->getCompleteName();
?>

Note

If class does not exist include will continue to run the rest of the script while requre will terminate when it cannot find the necessary file