13 OOP – IV in PHP
Hiren Joshi
Abstract class and method
- An abstract class is a class which cannot be used to create an object.
- An abstract class is used to create a superclass which can be inherited by other classes. But an object from superclass (Abstract class) cannot be created.
- An abstract method is a method which has only method name and parameter(s) but does not have code blocks which implements the method. In short, abstract method has defined but it cannot have implementation.
- An abstract method can only defined in abstract class.
- An Abstract class can have abstract and non-abstract method(s).
- A concrete class is a class which cane used to create an object.
- The concrete class which inherits the abstract class must implement all abstract methods of abstract class. Otherwise, PHP shows fatal error.
Following code shows an example of abstract class.
<?php
abstract class Person
{
private $fname,$lname,$email,$mobile;
public function __construct($fname,$lname)
{
$this->fname = $fname;
$this->lname = $lname;
}
//fname
public function getfname()
{
return $this->fname;
}
public function setfname($value)
{
$this->fname = $value;
}
//lname
public function getlname()
{
return $this->lname;
}
public function setlname($value)
{
$this->lname = $value;
}
public function getemail()
{
return $this->email;
}
public function setemail($value)
{
$this->email = $value;
}
//mobile
public function getmobile()
{
return $this->mobile;
}
public function setmobile($value)
{
$this->mobile = $value;
}
//fullname
abstract public function getfullname();
}
class Employee extends Person
{
private $eid, $edept;
public function __construct($fname, $lname,$eid,$edept)
{
$this->eid = $eid;
$this->edept = $edept;
parent::__construct($fname,$lname);
}
//eid
public function geteid()
{
return $this->eid;
}
public function seteid($value)
{
$this->eid = $value;
}
//edept
public function getdept()
{
return $this->edept;
}
public function setedept($value)
{
$this->edept = $value;
}
//getfullname
public function getfullname()
{
$fullname = $this->getfname().’ ‘.$this->getlname();
return $fullname;
}
}
$emp = new Employee(‘first’,’last’,1,’IT’);
print_r($emp);
$ans = $emp->getfullname();
echo “<br> $ans”;
?>
The output will be:
Employee Object ( [eid:Employee:private] => 1 [edept:Employee:private] => IT [fname:Person:private] => first [lname:Person:private] => last [email:Person:private] => [mobile:Person:private] => ) first last
Final class and method
- Sometimes you may be required that a method does not override in subclass. To do that, you can use the final keyword.
- Sometimes you may be required that a class does not inherited by a subclass. To do that, you can use the final keyword.
- Final class cannot be extended by a subclass.
Following example shows the use of final method.
<?php
class Person
{
private $fname,$lname,$email,$mobile;
public function __construct($fname,$lname)
{
$this->fname = $fname;
$this->lname = $lname;
}
//fname
public function getfname()
{
return $this->fname;
}
public function setfname($value)
{
$this->fname = $value;
}
//lname
public function getlname()
{
return $this->lname;
}
public function setlname($value)
{
$this->lname = $value;
}
public function getemail()
{
return $this->email;
}
public function setemail($value)
{
$this->email = $value;
}
//mobile
public function getmobile()
{
return $this->mobile;
}
public function setmobile($value)
{
$this->mobile = $value;
}
final public function getfullname()
{
echo “<h1> Hello”;
}
}
class Employee extends Person
{
private $eid, $edept;
public function __construct($fname, $lname,$eid,$edept)
{
$this->eid = $eid;
$this->edept = $edept;
parent::__construct($fname,$lname);
}
//eid
public function geteid()
{
return $this->eid;
}
public function seteid($value)
{
$this->eid = $value;
}
//edept
public function getdept()
{
return $this->edept;
}
public function setedept($value)
{
$this->edept = $value;
}
public function getfullname()
{
return $this->getfname(). ‘ ‘.$this->getlname();
}
}
$emp = new Employee(‘first’,’last’,1,’IT’);
print_r($emp);
$emp->setmobile(1234567890);
echo “<br>”;
print_r($emp);?>
The output will be:
Fatal error: Cannot override final method Person::getfullname() in :\wamp\www\PathshalaWAD\OOP\Final method\final method.php on line 92
If you define
<?php
final class Person
{
private $fname,$lname,$email,$mobile;
public function __construct($fname,$lname)
{
$this->fname = $fname;
$this->lname = $lname;
}
//fname
public function getfname()
{
return $this->fname;
}
public function setfname($value)
{
$this->fname = $value;
}
//lname
public function getlname()
{
return $this->lname;
}
public function setlname($value)
{
$this->lname = $value;
}
public function getemail()
{
return $this->email;
}
public function setemail($value)
{
$this->email = $value;
}
//mobile
public function getmobile()
{
return $this->mobile;
}
public function setmobile($value)
{
$this->mobile = $value;
}
final public function getfullname()
{
echo “<h1> Hello”;
}
}
class Employee extends Person
{
private $eid, $edept;
public function __construct($fname, $lname,$eid,$edept)
{
$this->eid = $eid;
$this->edept = $edept;
parent::__construct($fname,$lname);
}
//eid
public function geteid()
{
return $this->eid;
}
public function seteid($value)
{
$this->eid = $value;
}
//edept
public function getdept()
{
return $this->edept;
}
public function setedept($value)
{
$this->edept = $value;
}
public function getfullname()
{
return $this->getfname(). ‘ ‘.$this->getlname();
}
}
$emp = new Employee(‘first’,’last’,1,’IT’);
print_r($emp);
$emp->setmobile(1234567890);
echo “<br>”;
print_r($emp);?>
Then the output will be:
Fatal error: Class Employee may not inherit from final class (Person) in \wamp\www\PathshalaWAD\OOP\Final method\final class demo.php on line 92
Interface
- Some OOP language like C++ supports multiple inheritance.
- Multiple inheritance means a class can simultaneously inherits more than one class.
- In PHP, a class cannot simultaneously inherits more than one class.
- A class can inherit multiple interfaces simultaneously in PHP.
- An interface defines public method(s) which can be implemented by a class.
- The interface only defines the method (method name and parameter list) but does not provide method implementation (code to implement method).
- Each method in interface must be public.
- Method(s) in interface cannot be static.
- A class which implements interface must provide implementation of all the methods define in interface.
- An interface can define class constant also. These class constants can be available to any class which implements interface.
- A class can only inherit one class but it can implements many interfaces.
- A class can inherit one class and multiple interfaces simultaneously.
Following code shows example of Interface.
<?php
// interface showable interface showable
{
public function show();
}
//interface test
interface test
{
public function disp1($val1);
public function disp2($val1, $val2);
}
//interface gender
interface gender
{
const M = ‘Male’;
const F = ‘Female’;
}
// class person class Person
{
private $fname,$lname,$email,$mobile;
public function __construct($fname,$lname)
{
$this->fname = $fname;
$this->lname = $lname;
}
//fname
public function getfname()
{
return $this->fname;
}
public function setfname($value)
{
$this->fname = $value;
}
//lname
public function getlname()
{
return $this->lname;
}
public function setlname($value)
{
$this->lname = $value;
}
public function getemail()
{
return $this->email;
}
public function setemail($value)
{
$this->email = $value;
}
//mobile
public function getmobile()
{
return $this->mobile;
}
public function setmobile($value)
{
$this->mobile = $value;
}
}
class Employee extends Person implements showable,test
{
private $dept, $salary;
public function __construct($fname,$lname,$dept,$salary)
{
parent::__construct($fname,$lname);
$this->dept = $dept;
$this->salary = $salary;
}
//dept
public function getdept()
{
return $this->dept;
}
public function setdept($value)
{
$this->dept = $value;
}
//salary
public function getsalary()
{
return $this->salary;
}
public function setsalary($value)
{
$this->salary = $value;
}
// implements show mrthod of interface showable public function show()
{
echo “<br> Full Name :”. $this->getfname().’ ‘.$this->getlname(); echo “<br> Dept :”.$this->dept;
echo “<br> Salry :”.$this->salary;
}
public function disp1($val)
{
echo “<h1> This is disp1 function : $val”;
}
public function disp2($val1,$val2)
{
echo “<br> Calling Disp2 to display $val1 and $val2”;
}
}
$emp = new Employee(‘First’,’Last’,’IT’,25000);
echo “<br>”;
emp->show();
echo “<br>”;
$emp->disp2(‘Good Morning’,’from Disp2′);
echo “<br>”;
$emp->disp1(‘Greetings’);
?>
The output will be:
Full Name :First Last
Dept :IT
Salry :25000
Calling Disp2 to display Good Morning and from Disp2
This is disp1 function : Greetings
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