Oop in php lecture 2

1. © Copyright 2012 Hidaya Trust (Pakistan) ● A Non-Profit Organization ● www.hidayatrust.org / www,histpk.org
Interface
• Interface is an empty class which contains only the
declaration of methods.
• So any class which implements this interface must
contain the declared functions in it.
• Interface is nothing but a strict ruling, which helps to
extend any class and strictly implement all methods
defined in interface.
• A class can use any interface by using the implements
keyword.
• In interface you can only declare methods, but you
cannot write their body.
• That means the body of all methods must remain blank.
• One of the reasons is it implies strict rules while creating
a class.

2. © Copyright 2012 Hidaya Trust (Pakistan) ● A Non-Profit Organization ● www.hidayatrust.org / www,histpk.org
Interface Cont…
<?
//interface.dbdriver.php
interface DBDriver
{
public function connect();
public function execute($sql);
}
?>
• Did you notice that the functions are empty in an interface? Now let's
create our MySQLDriver class, which implements this interface.
<?
//class.mysqldriver.php
include("interface.dbdriver.php");
class MySQLDriver implements DBDriver
{
}
?>
• Now if you execute the code above, it will Fatal error, since we have
not implemented all methods in child class.

3. © Copyright 2012 Hidaya Trust (Pakistan) ● A Non-Profit Organization ● www.hidayatrust.org / www,histpk.org
Interface Cont…
<?
include("interface.dbdriver.php");
class MySQLDriver implements DBDriver
{
public function connect()
{
//connect to database
}
public function execute($query)
{
//execute the query and output result
}
}
?>
• Let's rewrite our MySQLDriver class as follows.

4. © Copyright 2012 Hidaya Trust (Pakistan) ● A Non-Profit Organization ● www.hidayatrust.org / www,histpk.org
Abstract Classes
• An abstract class is almost the same as interface.
• Except that now the methods can contain body.
• An abstract class must also be "extended", not "implemented".
• If the extended classes have some methods with common
functionalities, then you can define those functions in an abstract
class.
<?
//abstract.reportgenerator.php
abstract class ReportGenerator
{
public function generateReport($resultArray)
{
//write code to process the multidimensional result array and
//generate HTML Report
}
}
?>

5. © Copyright 2012 Hidaya Trust (Pakistan) ● A Non-Profit Organization ● www.hidayatrust.org / www,histpk.org
Abstract Classes Cont…
• Please note that we can use the abstract class and implement an
interface.
• Similar to declaring a class as abstract, you can also declare any
method as abstract.
• When a method is declared as abstract, it means that the subclass
must override that method.
<?
include("interface.dbdriver.php");
include("abstract.reportgenerator.php");
class MySQLDriver extends ReportGenerator implements DBDriver
{
public function connect()
{
//connect to database
}
public function execute($query)
{
//execute the query and output result
}
/ / you need not declare or write the generateReport method here you need not declare or write the
generateReport method here
//again as it is extended from the abstract class directly."
}
?>

6. © Copyright 2012 Hidaya Trust (Pakistan) ● A Non-Profit Organization ● www.hidayatrust.org / www,histpk.org
Abstract Classes Cont…
• Please note that we can use the abstract class and implement an
interface.
• Similar to declaring a class as abstract, you can also declare any
method as abstract.
• When a method is declared as abstract, it means that the subclass
must override that method.
<?
include("interface.dbdriver.php");
include("abstract.reportgenerator.php");
class MySQLDriver extends ReportGenerator implements DBDriver
{
public function connect()
{
//connect to database
}
public function execute($query)
{
//execute the query and output result
}
/ / you need not declare or write the generateReport method here you need not declare or write the
generateReport method here
//again as it is extended from the abstract class directly."
}
?>