WEBVTT 00:00.710 --> 00:01.220 Okay. 00:01.220 --> 00:05.720 It's finally the time that we learn about the objects and classes. 00:05.870 --> 00:10.430 First, let me use a metaphor to explain objects and classes. 00:10.580 --> 00:13.850 So class is like a boiler plate of a car. 00:13.880 --> 00:16.580 Let's say it is a boiler plate on. 00:16.580 --> 00:19.130 How do you build Tesla model Y? 00:19.160 --> 00:22.280 So you can think of this as a generic concept. 00:22.280 --> 00:28.910 When you are talking about a Tesla model Y, you don't mean my Tesla or your Tesla. 00:28.940 --> 00:31.040 You generally mean the car. 00:31.070 --> 00:37.820 But then an object is basically an instance of this Tesla model Y. 00:37.820 --> 00:44.150 And when we are talking about objects, I'm talking about my Tesla, which can have its own mileage 00:44.180 --> 00:46.820 or its own acceleration. 00:47.090 --> 00:54.740 And also we might be talking about your Tesla, which might have a different color, different mileage, 00:54.740 --> 00:55.730 etc.. 00:55.730 --> 00:59.540 So that's the main difference between objects and classes. 00:59.570 --> 01:09.550 Now you just define this boilerplate by using classes and then create objects based on those boilerplates. 01:09.580 --> 01:17.020 Now let's create a boilerplate which is a class, and let's make it a person. 01:17.050 --> 01:21.460 Now the classes can have data or methods. 01:21.460 --> 01:27.550 Data is basically class variables and methods are class functions. 01:27.550 --> 01:33.610 So in case of person we can have a string name. 01:34.630 --> 01:41.050 And also another property as it's also called can be age. 01:41.320 --> 01:47.920 Now we know that every person has a name and every person has an age. 01:47.920 --> 01:54.400 But once we create an object from this class, we are talking about my name, which is Pyotr, and my 01:54.430 --> 01:57.250 age, which currently is 37. 01:58.420 --> 02:02.010 So this is a field That's the type of that field. 02:02.010 --> 02:04.920 And this is the visibility keyword. 02:04.920 --> 02:07.050 Let's make everything public for now. 02:07.050 --> 02:10.200 And I'm gonna go back to this later on. 02:11.130 --> 02:13.140 Next up we can have methods. 02:13.140 --> 02:18.960 So methods are basically functions which also have this visibility keyword. 02:19.110 --> 02:24.780 So let's make an introduce method which would return a string. 02:25.170 --> 02:28.500 And this would be something pretty simple. 02:28.500 --> 02:36.180 It's just gonna say hi but we're going to use this data this field that we've defined above. 02:36.180 --> 02:44.370 So the main difference between using just functions and classes and objects is that when you have an 02:44.370 --> 02:50.820 object, you don't really have to pass around the data to all the functions, because those objects 02:50.820 --> 02:55.620 will just have its own data, like its own name and own age. 02:56.070 --> 03:02.600 And to access those, we're going to use a special variable called this and it refers to this current 03:02.630 --> 03:03.650 object. 03:03.650 --> 03:07.790 And we use the arrow operator to get the name. 03:07.880 --> 03:10.760 And I can also say that I am. 03:13.160 --> 03:16.820 Specific age years old. 03:17.300 --> 03:17.600 Okay. 03:17.600 --> 03:19.460 So that was a class definition. 03:19.460 --> 03:21.950 Now let's create an object out of this. 03:21.950 --> 03:24.140 So I can have a person variable. 03:24.140 --> 03:29.600 And I can make a new person using the new keyword, after which goes the class name. 03:30.470 --> 03:39.650 Next up I can access the public fields and public methods of this created object, because person variable 03:39.650 --> 03:45.110 is now an object, an instance of the class using the arrow operator. 03:45.410 --> 03:49.070 So I can call the introduce method. 03:49.910 --> 03:53.660 So let's see what would be the output. 03:54.320 --> 04:03.850 Well we actually got a fatal error that we are accessing a typed property that wasn't really initialized. 04:05.890 --> 04:07.660 Well, actually, that's the case. 04:07.660 --> 04:12.370 We haven't initialized those properties and we try to read their value. 04:12.400 --> 04:17.440 So let's see what's the typical way in classes to initialize values? 04:17.470 --> 04:23.890 Well, every single class can have a special method that is called constructor. 04:24.520 --> 04:33.340 Now constructor is just a function but it has a special name it's underscore underscore construct. 04:34.450 --> 04:40.930 And this will be always called whenever you create a new object using the new operator. 04:40.930 --> 04:44.740 It's just called automatically implicitly. 04:44.830 --> 04:52.990 And this constructor can accept some parameters like name and age. 04:53.680 --> 04:58.660 And we can use this to initialize the data of this object. 04:58.660 --> 05:04.470 So this name will equal name and this age will equal age. 05:04.500 --> 05:07.710 Now when we create the objects we can pass parameters. 05:07.710 --> 05:12.960 And the parameters are accepted here are same as in the constructor. 05:13.440 --> 05:17.460 So there should be a name I can do a lease. 05:18.210 --> 05:21.300 And let's say that Alice is 30. 05:21.300 --> 05:25.590 And when I run this now we've got this message. 05:25.590 --> 05:28.920 I am Alice and I am 30 years old. 05:30.120 --> 05:32.580 Now let me create a person. 05:32.580 --> 05:34.020 Number two. 05:34.050 --> 05:43.020 And this would be me this time so that we can see the difference. 05:45.870 --> 05:51.210 That this object has completely different data inside. 05:53.520 --> 05:56.820 So this is for Alice and this is for me. 05:58.670 --> 06:07.460 So the way this constructor is written where you pass something to the class and this is initializing 06:07.460 --> 06:11.780 the object data is something super common. 06:11.780 --> 06:18.800 One of the most common things that you're gonna do, you just need to pass some initial data to the 06:18.800 --> 06:20.120 created object. 06:20.150 --> 06:29.690 Now this was so common that in PHP eight a constructor property promotion was introduced. 06:29.690 --> 06:35.000 I spelled that slowly because this is how it is called professionally. 06:35.210 --> 06:43.700 And thanks to constructor property promotion, you don't really have to do this data initialization 06:43.700 --> 06:48.890 in a constructor, which can be cumbersome and lazy. 06:48.890 --> 06:53.060 People don't like cumbersome, daunting tasks. 06:53.450 --> 07:02.200 Now I can remove that and to promote this to properties, I can just add visibility keywords next to 07:02.230 --> 07:04.840 the constructor arguments. 07:04.840 --> 07:12.280 And then I also don't need to define or I can't define those properties right here. 07:12.430 --> 07:21.760 Now having those constructor property promotion is essentially the same as having the properties defined 07:21.760 --> 07:26.140 and initializing them explicitly in a constructor. 07:26.260 --> 07:34.690 So in cases where you don't really need to do anything extra with the past data, because this is why 07:34.690 --> 07:43.060 you can still pass the arguments through constructor and assign them to the data to the fields. 07:43.120 --> 07:52.180 You just might need to do something extra, but if you don't, then that's exactly the same thing and 07:52.180 --> 07:53.860 it's more concise. 07:54.130 --> 07:57.820 If we run this code again, it still works.