DAY 07 | PHP AND MYSQL | VI SEM | B.CA | CLASS AND OBJECTS IN PHP | L1

Summary

This video script introduces the fundamental concepts of object-oriented programming in PHP, focusing on classes and objects. It explains that a class serves as a blueprint for creating objects, which are instances with unique states and behaviors. The script demonstrates how to define classes, use constructors, and create objects. It also covers the concept of inheritance, allowing new classes to acquire properties from existing ones, and highlights PHP's support for single inheritance only. The faculty aims to educate students on creating reusable code and enhancing their understanding of PHP's object-oriented features.

Takeaways

• 📘 The script introduces the concept of classes and objects in PHP, emphasizing that a class is a blueprint or template for creating objects, which are instances with their own state and behavior.
• 🔑 The keyword 'class' is used in PHP to define a class, and the class name is user-defined, followed by a constructor method that has the same name as the class.
• 👨‍🏫 The script is part of a lecture series on object-oriented programming in PHP, delivered by a faculty member from the Department of Computer Science.
• 🏗️ PHP supports object-oriented programming concepts such as classes, objects, polymorphism, data abstraction, and data encapsulation.
• 📝 The script provides an example of creating a class in PHP, including the use of access modifiers like private, public, and protected, and demonstrates how to define properties and methods within a class.
• 🎯 The constructor in a class is a special method that is automatically executed when an object of that class is created, often used for initializing properties.
• 🧬 Inheritance in PHP is discussed as a way to reuse properties from one class in another, with the 'extends' keyword used to create a child class that inherits from a parent class.
• 🔄 PHP supports only single inheritance, meaning a class can inherit from only one parent class, but multiple inheritance can be achieved through multiple single inheritances.
• 📝 An example of single inheritance is given, where a child class acquires the properties and methods of a parent class, allowing access to both the parent's and child's functionalities.
• 📑 The script includes a practical example of creating objects and accessing their properties and methods, demonstrating how to instantiate a class and interact with its members.
• 🔚 The lecture concludes with a teaser for the next session, which will cover form handling in PHP, including different methods supported for form processing.

Q & A

What is the definition of a class in PHP?

A class in PHP is a blueprint or template that outlines the structure and behavior of an object. It defines a set of properties and methods that objects of that class can have.

How do you create a class in PHP?

To create a class in PHP, you start with the keyword 'class' followed by the class name and use curly braces to enclose the properties and methods of the class.

What is the purpose of a constructor in a class?

A constructor in a class is a special method that is automatically executed when an object of that class is created. It is used to initialize the properties of the object.

What is an object in the context of PHP?

An object in PHP is an instance of a class. It represents a specific entity with its own properties (attributes or variables) and can execute methods (functions or behaviors) defined in the class.

How do you create an object of a class in PHP?

In PHP, you create an object of a class using the 'new' keyword followed by the class name and calling the constructor with the appropriate parameters if needed.

What is inheritance in PHP?

Inheritance in PHP is a feature that allows a new class to inherit properties and methods from an existing class. It promotes reusability and reduces code duplication.

What is the difference between a parent class and a child class in PHP?

In PHP, a parent class (also known as a base class or superclass) is the class from which another class inherits. A child class (also known as a derived class or subclass) is the class that inherits properties and methods from the parent class.

How do you implement single inheritance in PHP?

In PHP, you implement single inheritance by using the 'extends' keyword to create a new class that extends the properties and methods of an existing class.

Why is inheritance important in object-oriented programming?

Inheritance is important in object-oriented programming because it allows for code reusability, promotes a hierarchical structure, and enables the creation of specialized classes based on more general classes.

What is the limitation of inheritance in PHP compared to other languages?

PHP supports only single inheritance, meaning a class can inherit from only one parent class at a time. This is a limitation compared to some other object-oriented languages that support multiple inheritance.

How can you access methods of a parent class from a child class in PHP?

In PHP, you can access methods of a parent class from a child class by creating an object of the child class and then calling the parent class methods using the object and the appropriate syntax.

Outlines

00:00

📚 Introduction to Class and Object in PHP

The speaker introduces the concept of objects, describing them as entities with their own state and behavior. The session will cover class objects and inheritance in PHP. A class in PHP is likened to a blueprint or template that defines the structure and behavior of objects. The speaker explains that PHP is an object-oriented programming language, supporting key concepts like classes, objects, polymorphism, data abstraction, and encapsulation.

05:04

🔧 Creating Classes in PHP

This section explains how to create a class in PHP using the 'class' keyword and provides an example of a classroom setup to illustrate the concept. A class is described as a group of objects sharing common properties. The speaker discusses the importance of a class as a template that contains variables and methods. The process of creating an object from a class is explained, emphasizing how an object can access the class's methods and variables.

10:07

🔄 Understanding Objects and Instances

The speaker delves into the concept of objects in object-oriented programming, defining an object as an instance of a class, representing a specific entity or concept in the code. Objects have properties (attributes or variables) and can execute methods (functions or behaviors). The example code provided demonstrates how to create an object in PHP using a user-defined class and the 'new' keyword, followed by an explanation of how to access and manipulate object properties.

15:07

🔗 Introduction to Inheritance in PHP

This section introduces the concept of inheritance, which allows for the reuse of properties and methods from one class (the parent class) in another class (the child class). The speaker explains the use of the 'extends' keyword in PHP to implement inheritance and illustrates the concept with an example. The limitations of inheritance in PHP are discussed, such as the support for single inheritance only, while multiple inheritance can be achieved using a combination of single inheritances.

20:09

🔚 Conclusion and Preview of Next Session

The session concludes with a summary of the topics covered, including the definitions of classes and objects, as well as how to implement inheritance in PHP. The speaker previews the next session, which will focus on form handling in PHP, discussing how to create forms and the different methods available in PHP for handling form data. The speaker thanks the students and encourages them to continue learning.

Keywords

💡Object

In the context of the video, an 'Object' refers to an entity with its own state and behavior. It is a fundamental concept in object-oriented programming (OOP), representing a specific instance of a class. For example, in the script, a 'pen' is used to illustrate an object, with attributes like type, color, and width defining its state.

💡Class

A 'Class' is defined as a blueprint or template for creating objects in OOP. It outlines the structure and behavior of the objects, including their properties and methods. In the script, the class is used to represent a concept such as a 'classroom', which includes elements like a 'blackboard', 'students', 'chairs', and 'benches'.

💡Inheritance

Inheritance is a core concept in OOP that allows a new class to acquire the properties of an existing class. It is about reusability and is used to avoid code duplication. In the script, inheritance is discussed in the context of extending features from a 'parent class' to a 'child class', such as creating a 'Rectangle' class that inherits properties from a 'Shape' class.

💡Constructor

A 'Constructor' is a special method in a class that is automatically executed when an object of that class is created. It is used to initialize the object's state. The script provides an example of a constructor in the 'Rectangle' class, which takes parameters to set the 'length' and 'width' of the rectangle upon creation.

💡Method

A 'Method' in OOP is a function that is associated with an object and defines the behavior of the object. In the script, methods are used to perform actions like calculating the 'perimeter' and 'area' of a rectangle, demonstrating how objects can execute behaviors defined by their class.

💡Property

A 'Property' in the context of OOP refers to the attributes of an object, representing its state. The script mentions properties in the context of a class, such as the 'length' and 'width' of a rectangle, which are properties that define the state of the object.

💡Instance

An 'Instance' is a specific occurrence of an object created from a class. It represents a single entity with its own set of properties and methods. The script explains that an object is an instance of a class, such as a 'pen' being an instance of a 'WritingInstrument' class.

💡Access Modifier

Access modifiers in OOP are used to control the accessibility of class members, such as variables and methods. The script mentions 'private', 'public', and 'protected' as types of access modifiers, which determine where and how class members can be accessed, like making the 'length' and 'width' of a rectangle private to restrict access from outside the class.

💡Polymorphism

Although not explicitly mentioned in the script, 'Polymorphism' is a concept in OOP that allows objects of different classes to be treated as objects of a common superclass. It is related to the video's theme as it is one of the fundamental concepts of OOP alongside classes, objects, and inheritance.

💡Encapsulation

Encapsulation is the practice of bundling the data (attributes) and methods that operate on the data into a single unit or class. It is also not directly mentioned in the script but is a key principle of OOP. It is related to the script's discussion of classes as templates that encapsulate the state and behavior of objects.

Highlights

Definition of object-oriented programming language and its support for concepts like class, object, polymorphism, data abstraction, and data encapsulation.

Explanation of class as a blueprint or template for creating objects.

Description of object as an entity with its own state and behavior.

Introduction to creating a class in PHP using the 'class' keyword.

Discussion on access modifiers: private, public, and protected in PHP classes.

Explanation of a Constructor as a special method in a class with the same name as the class.

Example of creating a class with a parameterized Constructor in PHP.

Demonstration of creating a class with methods to calculate perimeter and area.

Process of creating an object in PHP and accessing its methods and variables.

Introduction to inheritance as a concept for reusability in object-oriented programming.

Differentiation between parent class (super class, base class) and child class (sub class, derived class).

Syntax and implementation of single inheritance in PHP using the 'extends' keyword.

Example of creating a child class that inherits properties from a parent class.

Explanation of how to access methods of both parent and child classes through an object.

Reasoning behind using single inheritance for code reusability in PHP.

Announcement of the next session's topic: form handling in PHP.

Conclusion and thank you note to the students for attending the session.

Transcripts

so what is object object is nothing but

an entity it's going to have its own

state and its own behavior to create a

class in PHP I'm using the keyword class

okay I'm going to use the keyword called

class if I want to inherit the features

from one class to another what I want to

do I want to extend the parent class to

my child

[Music]

class

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hello to all a warm welcome to my new

unit and the unit name here is class

ired objects in PHP I'm your reati M

faculty from the Department of computer

science vidyashram first grade College

the Temple of Excellence mauru so dear

student in my today's session I'm going

to deal with class objects as well as

inheritance so dear student we all are

familiar with the concept like class and

object what is class and what is object

so dear Student please make a note here

PHP is example for objectoriented

programming language so when I say

objectoriented programming language then

it must support the concepts like class

object polymorphism data abstraction

data encapsulation and so on now if I

consider class what is a class class is

nothing but a blueprint or template and

if I consider object object is nothing

but the instance or functions of the

class or instance of a class okay fine

anyway we will discuss all those things

in depth in my today's session so what

is class class is nothing but a group of

object in simple word I can tell it is a

template okay fine let me to consider

the example here to create a class I'll

start with the keyword class okay fine

now think that okay I'm taking the class

for six same BCA so sixth same B

CA okay fine if I consider the

classroom okay what are the thing I have

I have the board

black board okay fine then I have the

students okay fine then along with

student I have the okay chairs as well

as benches so a class what is class

class is just a template okay class is

just a template or it's a blueprint okay

fine where I'm going to have all the all

the

what variables as well as methods okay

so if I want to access the variables and

methods what I want to do I want to

create a object of the class with the

help of the object I can able to access

the methods and variables of the class

so a class is a group of objects which

have common property so which can have

the common property in simple word it is

a template or it is a blueprint from the

class I can able to create a object so

we can able to create a object so an

entity class is what it's a entity that

can have the state and and behavior okay

fine if I consider object object can

have the state and behavior and it is

known as object so what is object object

is nothing but an entity it's going to

have its own state and its own

behavior okay fine for example if I

consider chair bike marker pen tables

Etc so it's going to have its own state

as well as Behavior okay fine if I

consider this recording room as my class

okay then I can have the objects like

board okay I can have the objects like

pen okay if I consider this pen okay so

the type of pen color of pen width of

pen dimension of pen okay these are

nothing but the okay objects okay fine a

class is a fundamental concepts in PHP

okay it's mainly act as a blueprint or a

template and that outlines the structure

and behavior of the object so who is

going to define the structure and

outline of the object that is none other

than the class so class act as a

foundation for creating the object to

specific type by providing a set of pred

define properties and methods in simple

word what is class class is a blueprint

or it is a template okay so by using

class I can able to create a object

object is nothing but the

entity okay fine now creating a class in

PHP involves the class keyword in the

sense what if I want to create class in

PHP I want to start with the keyword

word called class at the same time what

I want to do I want to specify the user

defined class name a class can also have

a

Constructor in the sense what what is

Constructor Constructor is nothing but

the method okay it's a special method

whose name is same as the class name so

dear student let me to write the class

here to create class I'm going to use

the key word called class and a is

nothing but the class name and if I have

a

method okay same as class name then it

is called as Constructor so class can

have the

Constructor The Constructor of the class

is a special method it's a special

method okay it is automatically executed

when an object is Created from that

class when I create a object of that

class what's going to happen the

constructors are automatically

executed so if I consider this one okay

this is the example for the class how I

can able to create a class in PHP so

I'll start with the PHP okay and I'll

write the keyword called class and here

person is nothing but the class name

what kind of class name it is nothing

but the user defined class name and and

start with the flare bracket okay and I

can have the set of statements and I'm

going to close the flare bracket at the

same time I'm going to close the script

that's nothing but the PHP script okay

fine now see here I have very simple

example here okay so I have the class

called rectangle okay in that okay what

is this private private public that's

nothing but the access modifier so if I

consider access modifier I can have the

three type of access

modifier private public and protected

and see here I have the variable called

length and I have the variable called

width and here I have the function and

in okay and in PHP okay I use a

Constructor okay I use a Constructor

structor and it takes the two parameters

and this is example for your

parameterized Constructor okay fine then

what I will do I'll assign the value to

the length Okay and at the same I'll

assign the value to the width okay fine

now I have one more function called

calculate perimeter okay so it's a

function so I'm going to use the keyword

function to create a function in PHP

what I want to do I want to use a

keyword called function and see this

function okay Returns the value so I'll

write return okay I'm going to find the

perimeter okay fine then what I want to

do once again I have the user defined

method called calculate area it's also

the function user defined function and

I'm going to calculate the area okay

this is the way I can able to create a

class in PHP okay fine now what is an

object till now we discussed how we can

able to create a class to create a class

in PHP I'm using the keyword class okay

I'm going to use the keyword called

class okay fine now what is object

object is nothing nothing but the

instance of an class so it's nothing but

the functionalities of an class so an

object oriented programming language an

object is a instance of the class so

what is instance instance is nothing but

the functionality okay it is nothing but

the

functionality it represents a specific

entity or Concept in our code so object

have its own properties properties in

the sense what that is nothing but the

attributes or variables okay and okay

can execute the methods it's also known

as functions or behavior so object can

have its own property as well as state

so here we discuss how to create an

object see here I have the dollar sign

okay variable so it is nothing but your

object name it is nothing but your

object name user defined object name

equal to new is a keyword okay and class

name so class name is nothing but your

okay see I have class name opening and

closing parenthesis what it indicates it

indicates it's a Constructor okay fine

now I have the small example code here

see we know that we are going to embed

PHP with the HTML so I'll start start

with HTML okay I'll start with the body

okay inside the body I'm going to create

a class what is my class name it's

nothing but the fruits okay fine now see

I have the variable called name and it's

of type public

so Apple okay now what I'm doing here

I'm creating the creating the object now

okay I'm creating the object Apple okay

how new it is your class name what's my

class name fruit what kind of

Constructor it is default Constructor so

it is default Constructor or no

parameterized

Constructor now Apple okay with the help

of object okay using Arrow operator I'm

going to call the name okay and I'm

going to assign the string called Apple

I'm assigning Apple now if I want to

display uh the value apple or string

Apple what I will do I'll go with Echo

okay then what is this it is my object

Arrow operator and my variable name

called name then what I will do I'll

close the PHP script okay I'll close the

body and I'll close the HTML and what is

my output apple is my output okay okay

fine now I have the concept called

inheritance so what is inheritance

inheritance is nothing but the

reusability reusability in the sense

what when I want to reuse the property

what I will do I'll go with the

inheritance so whenever I want to

understand the concept like inheritance

you have to remember two things one is

your old class one is your new class

okay when I when the new class okay when

I create a new class using the old class

then it is called inheritance so I'm

going to derive a new class from the old

class that is known as

inheritance and in C++ Java or in our

net we have discussed inheritance there

we have discussed single inheritance

multiple inheritance multi-level

inheritance and hierarchical inheritance

but in PHP we can have only single

inheritance so it is a concept of

accessing the features of one class from

another class so it's a feature of

accessing from one class to another

class think that okay I have some

features in my old class okay and I want

to access that feature in my new class

that time what I will do I'll go with

the inheritance so if we inherit the

class features into another class we can

access both the class property so this

old class is called by the name super

class okay or it is called by the name

parent class or it is called by the name

Base Class and what about new class this

new class is nothing but the child class

okay okay or it's nothing but the sub

class or it is nothing but the derived

class okay it's nothing but the derived

class so if I want to inherit the

features from one class to another what

I want to do I want to extend the parent

class to my child class so what I will

do I'll go with the extend keyword okay

so I'll go with the extend key

and in PHP we can able to have only

single

inheritance even I can have multiple

inheritance that can be achieved by

using multiple single

inheritance so to implement inheritance

in PHP what I will do I'll go with the

extend keyword okay fine now let's

discuss the syntax here I have the class

called derived okay okay then extends

Base Class okay fine let me to draw the

single inheritance first see I have

the class A what is this it's my parent

class or super class or it is nothing

but the Base Class okay now I have the

child called b b can able to acquire the

property of a okay so it is nothing but

the sub class or child class or derived

class okay fine now first what I want to

do I want to create a class called a

okay it can have its own property okay

fine now okay I'm going to create a

class called B and this B extends

the property of a okay now we can have

all the properties of a in the sense

what all the Bel belongings of a now see

here class the child class is nothing

but the derived class okay I'll start

with the extend keyword and base class

is nothing but your parent class now I

can have the members and functions here

okay fine now okay so I'll start with

the this is just a syntax now now okay I

want to create a single inheritance so

where I create the single inheritance in

my PHP script so I'll start with the PHP

so what's my class name a is nothing but

the class name okay in this class I have

a function called F1 so what's my

function name F1 and I'm going to

display classes and objects so I'm just

going to convey the message that it is

just a class and object objects okay

fine now same thing I want to have in my

next class so what I will do I'm going

to extend the class so B is my child

class okay B is my child Class A is my

parent class I want to acquire the

properties of a in my B so Class B

extends a in this I have a function

called F2 then what about this function

it's a keyword used to create a function

in PHP and I'm going to have the message

called

PHP okay fine now what I will do okay

I'm going to create a object only for my

child class by using the object of child

class I can able to access the methods

and okay methods and variables of the

child class as well as the parent class

so with the help of object I'm going to

call a method of the parent class and

with the help of object I'm going to

call the method of child class so F1

method present in your parent class and

F2 method is present in your that is fun

two is present in your child class so

this is the way I can able to implement

single in inheritance so why I use

single inheritance it is mainly to reuse

the property so instead of writing same

code again and again what I can able to

do I can able to reuse the properties

for that I'm going to have the

inheritance okay fine and PHP supports

only single inheritance even I can have

the multiple inheritance by using single

inheritance anyway dear student in my

today's class I started with what is

class what is object and how I can able

to create a inheritance in my next class

I'm going to deal with okay I'm going to

deal with form handling in the sense how

I can able to create a forms in PHP what

are the different methods supported by

the PHP to handle the forms all those

things we will discuss in my next

session anyway dear student thank you

for watching my session and let's meet

in the next session with more

information about PHP until that keep

watching and keep learning thank you