[0:08] hello everyone i am anish from simply
[0:10] learn and welcome to the video on object
[0:13] oriented programming in php
[0:15] in this video we will discuss everything
[0:18] about oops concept in detail
[0:20] but before that let me tell you
[0:23] according to indeed.com the demand for
[0:25] php developers has massively increased
[0:28] to 835 percent since january 2020
[0:33] however in today's market it is the
[0:35] fastest growing tech job across the
[0:37] industry
[0:39] so in today's video we'll be discussing
[0:42] what is php what are the concepts of
[0:44] oops in php and finally we will have a
[0:47] look at the demo where we will be
[0:49] executing the code that has class
[0:51] objects inheritance and polymorphism in
[0:54] it
[0:55] now comes the important question what
[0:58] exactly is php
[1:01] so we have spoken a lot about it so far
[1:03] but do you know what it means
[1:05] well php stands for hypertext
[1:08] preprocessor
[1:09] it is a server-side scripting language
[1:11] that is embedded into html and used for
[1:14] developing dynamic websites
[1:17] now let's move ahead and understand the
[1:19] concepts of oops in php
[1:22] so as you can see on the screen i have
[1:24] listed down the eight concepts of oops
[1:27] that we will be discussing today
[1:29] first is class
[1:31] next comes objects then its member
[1:33] function and member variables then
[1:36] constructor and destructor
[1:38] inheritance and finally it is
[1:40] polymorphism
[1:42] now let's walk through each of the
[1:44] concepts one by one
[1:46] first is class
[1:48] it is a blueprint of an object that
[1:50] provides initial values for the state a
[1:54] class consists of both data and
[1:56] functions and data and functions
[1:57] together are called objects
[2:00] now let's first have a look at the class
[2:04] let me create a file
[2:06] named class dot php
[2:10] and let us write the code first
[2:52] um
[3:05] okay
[4:04] here i have defined a class by using the
[4:06] class keyword
[4:07] followed by fruit which is the class
[4:10] name
[4:11] next i have added a pair of curly braces
[4:14] and added the entire properties and
[4:16] methods within the braces so as you can
[4:19] see on the screen we have declared a
[4:21] class named fruit
[4:23] that contains two properties called name
[4:26] and color
[4:27] along with that i have also added two
[4:29] methods set name and get name
[4:34] now now the purpose of these methods is
[4:36] for setting and getting the name
[4:39] property
[4:40] so let me give you some in important
[4:42] information so when you define a class a
[4:45] variable in it is called property while
[4:48] a function is known as method
[4:51] now let us execute the code and see the
[4:53] output
[4:57] let's go to the browser
[4:59] and type localhost followed by the file
[5:02] name
[5:08] here here's a file class.php
[5:11] and as you can see on the screen
[5:13] the code is running perfectly
[5:16] now that was about the class
[5:19] next comes objects
[5:21] so it is an instance of a class
[5:23] basically
[5:25] a variable holds a date of a class
[5:27] now we define a class once
[5:31] and create as many objects in it
[5:34] for a better understanding let me give
[5:36] you an example
[5:37] suppose a car is a class so
[5:40] mercedes-benz and bmw would be objects
[5:43] now let's see objects
[5:45] classes are incomplete without objects
[5:48] so we can add as many objects as we want
[5:51] from a class
[5:52] and every single object has the
[5:55] properties and methods defined in the
[5:57] class but those objects will have
[5:59] different property values
[6:01] so objects of a class are created using
[6:04] the new keyword
[6:06] now let me open the code editor
[6:10] and let's create another file
[6:13] called
[6:14] obj.php
[6:18] so this code will be the same
[6:21] let's copy
[6:23] and paste it here
[6:28] now let me type the code for object
[6:33] [Music]
[6:41] as you can see i have used the new
[6:43] keyword to create object of the class
[6:46] fruit
[6:51] similarly
[6:56] banana
[6:57] would be another object
[7:11] and now we'll use the set name function
[7:16] to set
[7:17] the name to apple
[7:19] on this object on the apple object that
[7:22] we have created
[7:24] similarly
[7:25] we will
[7:27] set the name
[7:31] for the banana object
[7:44] there's an extra bracket here let's move
[7:46] it
[7:51] now moving forward let us type the code
[7:56] to display
[7:59] what we have added into the objects
[8:04] for this can you guess which method will
[8:07] be using
[8:09] yes the get name method
[8:12] will be used to display
[8:15] the name saved onto the object using the
[8:17] set name method
[8:40] now that our code is complete
[8:43] let us run and check
[8:46] if it's working correctly
[8:50] let me go back
[8:52] and refresh
[8:55] now here we have our object.php file
[9:00] yes the code runs perfectly the fruit
[9:02] program and it is displaying apple and
[9:04] banana from the two objects that we
[9:06] created i hope now you have clearly
[9:09] understood the concept
[9:11] moving on to the next one let's talk
[9:13] about the member variable and member
[9:15] function
[9:16] a member variable is defined within a
[9:18] class
[9:20] the data can be accessed by the member
[9:22] functions alone
[9:23] now once the object is built these
[9:25] variables are called attributes of the
[9:27] object whereas member function is
[9:30] defined within a class and is used to
[9:32] access object data
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[9:36] the battle what if you could do that for
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[9:41] the link in the description to know more
[9:44] so next comes constructor
[9:47] so it allows an individual to alert an
[9:50] object's properties
[9:52] while the object creation
[9:54] while a destructor is a function that is
[9:56] called when the object stops working
[9:59] we will have a look at the constructor
[10:02] program
[10:03] so constructor allows an individual to
[10:05] alert an object's properties while the
[10:08] object creation
[10:09] now suppose you build a program using
[10:11] constructor function
[10:13] php will automatically call the
[10:15] construct function while creating an
[10:17] object from a class also remember that
[10:20] when you write the construct function
[10:22] always prefix it with two underscores
[10:26] now let's have a look at the example
[10:28] where we will be using a constructor
[10:30] function with calling the set name
[10:31] method
[10:33] now this set name function is often used
[10:36] when you assign a value to the name
[10:37] attribute
[10:40] now let's open the code editor and
[10:43] create a constructor file
[10:54] [Music]
[11:11] we'll again create the two properties
[11:14] named
[11:16] name
[11:19] and color
[11:22] now we will create a constructor
[11:25] with two underscores
[11:27] and a construct keyword
[11:30] and i'll give the two properties as
[11:33] attributes to the constructor
[11:39] now in this
[11:41] program we'll be using the constructor
[11:43] function
[11:46] as the set
[11:48] method
[11:49] to set the names
[11:52] and color of a fruit by default
[11:56] during the object creation itself
[12:08] we still need to create the get
[12:11] functions
[12:29] so
[12:41] now let's create an object to invoke the
[12:44] constructor
[12:54] now since the constructor has attributes
[12:56] we will have to give the values for the
[12:59] attributes as well
[13:01] so the fruit would be
[13:03] strawberry
[13:06] and
[13:07] color
[13:08] would be pink
[13:11] so this creates a new object and it
[13:14] gives
[13:16] the values to the constructor
[13:33] uh
[13:58] in the php script
[14:01] and
[14:02] our html code as well
[14:09] let us save the code and check if it's
[14:11] working
[14:14] let's go back
[14:16] refresh
[14:17] now constructor file is visible let's
[14:20] click on it and yes
[14:22] so
[14:23] when the object strawberry is created
[14:26] the attributes we have given to the
[14:28] constructor strawberry and the color
[14:31] pink were already
[14:33] assigned to it
[14:35] and it is displayed in the browser
[14:36] itself
[14:38] now that the constructor program is done
[14:40] next let's see an example of how a
[14:42] destructor works
[14:44] let's open the code editor
[14:47] create another file
[14:49] destructor.php
[14:52] now the destructor code will be very
[14:54] similar to the constructor one so we
[14:56] will copy the code
[14:57] into the destructor file and make some
[14:59] changes
[15:01] so
[15:02] let us remove this we don't need it
[15:07] and write our destructor function
[15:11] so destructive function is written
[15:13] similarly
[15:14] how constructor function is written
[15:17] so it starts with two underscores and a
[15:20] destruct keyword
[15:23] it does not have an attribute
[15:28] now why did we delete the get functions
[15:31] is because
[15:32] we will be using the destructor
[15:35] for it
[16:15] also we won't be needing this
[16:20] just the object creation is sufficient
[16:26] now let's save our program and
[16:30] do the drill again
[16:34] open the browser
[16:39] here a destructor file is visible
[16:42] and it shows the fruit strawberry and
[16:44] the color is pink so when the object
[16:47] function is complete
[16:50] and the program ends the destructor
[16:52] function is called which displays the
[16:55] strawberry and the color pink
[16:59] now
[17:00] comes inheritance so it derives new
[17:02] classes or child classes from the parent
[17:05] class
[17:06] however inheritance can have its own
[17:08] properties and methods too
[17:10] so inheritance has two classes
[17:13] first is parent class and the other one
[17:15] is a child class
[17:17] now let's talk about each of them in
[17:18] detail
[17:19] so parent class is otherwise called a
[17:22] base class that is inherited from
[17:24] another class
[17:26] and a child class is a subclass that
[17:28] inherits from another class
[17:31] a child class can have subclasses and
[17:34] derived classes
[17:35] now let's have a look at the inheritance
[17:37] program
[17:38] so the child class is derived from all
[17:41] the properties and methods from the
[17:43] subclass
[17:45] in addition it can have its own
[17:47] properties and methods too
[17:49] so an inherited class is defined by
[17:52] using the extends keyword
[17:54] let's look at an example
[17:57] open the code editor so i have taken the
[17:59] liberty to create the inheritance.php
[18:02] file
[18:03] and write some of the code that we have
[18:05] already written so i'll be writing only
[18:07] the code that is necessary for the
[18:09] inheritance part
[18:14] now also remember when you derive a
[18:17] child class from a parent class only the
[18:19] public methods are derived into the
[18:22] child class
[18:23] so we will be creating the methods as
[18:26] public
[18:27] in order them to be
[18:29] inherited
[19:17] made this function public
[19:27] let's
[19:28] end this class
[19:30] and create another class in order
[19:34] to inherit this class
[19:38] so we will name
[19:40] another class as
[19:43] cherry
[19:45] extends
[19:47] fruit
[19:52] and we'll create another function for
[19:56] cherry so this function is exclusive to
[19:58] cherry
[20:28] so we have given a message through this
[20:30] method
[20:32] now
[20:34] let's create an object
[20:37] cherry
[20:39] new
[20:40] cherry
[20:42] and
[20:45] give the values for the attributes
[20:47] of
[20:48] this constructor
[21:24] let's save the code
[21:26] and check if it's working
[21:35] well there seems to be an error
[21:38] now let's try to resolve it
[21:45] okay got it so we
[21:47] created the object
[21:51] within
[21:52] the cherry class so it got localized
[21:57] what we need to do is put that code
[21:59] outside of the cherry class
[22:02] and it should work fine now
[22:08] yes so is cherry a fruit or a berry a
[22:12] cherry is a fruit and the color of the
[22:13] fruit is red
[22:15] and now we will talk about the last
[22:17] concept that is polymorphism so
[22:20] polymorphism has many forms
[22:23] the same function is utilized for
[22:24] different purposes
[22:26] it has a class with a variety of
[22:28] functions simultaneously sharing a
[22:30] common interface
[22:33] so inherited methods are overridden by
[22:36] redefining the methods in the derived
[22:38] class now let me write the code to make
[22:42] it clear
[22:44] so already created the polymorphism php
[22:47] file
[22:48] i have copied the inheritance code
[22:51] into the polymorphism part
[22:54] and then now we'll make the changes into
[22:57] the derived class that is cherry
[23:03] so let's create a property named
[23:07] wait
[23:11] now to
[23:12] override the constructor and the intro
[23:16] function
[23:17] from the fruit class we will have to
[23:19] create the same functions
[23:21] in the derived class also
[23:35] now this function construct has got one
[23:39] extra attribute in comparison to this
[23:41] function construct
[23:50] okay
[24:24] let's create the intro function too
[25:30] now a code is ready
[25:32] let us create another object
[25:36] to invoke
[25:38] the functions
[26:10] now did you notice what we did here
[26:13] so
[26:13] when we created the object cherry for
[26:16] for the cherry class we gave three
[26:19] attribute values instead of two
[26:22] in order to invoke this construct
[26:24] function
[26:27] not this
[26:39] let us run it and check
[26:50] so it runs perfectly it displays the
[26:52] fruit the color and the weight
[26:56] now we have reached the end part of the
[26:58] video on the object-oriented programming
[27:00] in php
[27:02] i hope it was informative and
[27:04] interesting and if you have any queries
[27:06] about the topics covered in this video
[27:08] please ask away in the comment section
[27:10] below our experts are 24 7 ready to
[27:13] solve your queries thanks for watching
[27:16] stay safe and keep learning
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