WEBVTT 00:00.290 --> 00:00.680 Okay. 00:00.680 --> 00:06.050 So next up let's learn the anonymous functions also called closures. 00:06.110 --> 00:12.650 The main difference between the anonymous functions and the traditional functions is that the anonymous 00:12.650 --> 00:22.580 functions don't exist under a specific name, which means that you need to assign this anonymous functions 00:22.580 --> 00:30.560 either to a variable, or you need to pass it as a parameter to a function. 00:31.010 --> 00:34.100 It can't really exist on its own. 00:34.100 --> 00:36.500 That's the main conclusion. 00:36.500 --> 00:44.390 And in PHP, like in many other languages, functions are called first class citizens. 00:44.390 --> 00:48.980 What this means is exactly what I've described a second ago. 00:48.980 --> 00:56.150 This means you can assign functions to variables or pass them around as function arguments. 00:56.570 --> 01:00.180 Okay, so that's a little bit of theory. 01:00.210 --> 01:05.250 Now let's jump to the code editor and let's see some examples. 01:05.250 --> 01:14.490 Let's just call this anim PHP and let's see some anonymous functions also called closures. 01:15.690 --> 01:18.510 So let's create an anonymous function. 01:18.510 --> 01:22.860 And it will accept a name parameter. 01:23.370 --> 01:29.550 And it will simply return the hello text with the name. 01:30.990 --> 01:32.820 Now let me add a semicolon here. 01:32.820 --> 01:36.720 And well how do we call this function. 01:36.990 --> 01:37.560 Yes. 01:37.560 --> 01:38.730 So that's the problem. 01:38.760 --> 01:43.050 The anonymous functions or closures as they are also called. 01:43.080 --> 01:46.320 They don't exist under a given name. 01:46.320 --> 01:55.770 That's why you need to associate them with something like associate them with a variable like this greet 01:55.770 --> 01:56.610 variable. 01:56.610 --> 02:09.390 Now this variable is essentially the function name and to call it I can echo, greet and say maybe David. 02:11.700 --> 02:15.390 Now let me call this, uh, this is anon PHP. 02:15.570 --> 02:18.120 As you see, this has worked fine. 02:20.610 --> 02:20.910 Okay. 02:20.910 --> 02:23.730 So let's see yet another example. 02:24.210 --> 02:29.160 This time we won't be associating the anonymous function to a variable. 02:29.160 --> 02:33.180 Instead we're going to pass it to another function. 02:33.210 --> 02:37.020 First things first, let's create some example data. 02:37.050 --> 02:39.330 This would be this numbers array. 02:39.360 --> 02:43.830 We're gonna calculate the square of every element in this array. 02:43.830 --> 02:48.570 And the result will be put into a new array. 02:49.530 --> 02:51.510 Let's call it squared. 02:51.540 --> 02:56.580 Now we are gonna use an array map function. 02:56.610 --> 03:06.070 This is a built in PHP function that will call our anonymous function on every item in the array. 03:07.180 --> 03:14.230 So here we create an anonymous function in place and it's going to receive a number. 03:15.130 --> 03:19.960 And we're just going to return the number times number. 03:19.990 --> 03:22.300 This is how you calculate the square. 03:22.300 --> 03:27.070 And the second argument to array.map is the source array. 03:27.190 --> 03:29.860 This is our numbers. 03:32.290 --> 03:35.770 So this time I'm gonna call Vardump. 03:35.770 --> 03:38.350 So we also see the type. 03:38.470 --> 03:45.040 And let's output squared and maybe the numbers the original array. 03:45.070 --> 03:45.670 Okay. 03:45.700 --> 03:47.110 Let me run it. 03:47.350 --> 03:51.010 That's the original array 123 the numbers. 03:51.010 --> 03:55.570 And here we've got the squares of every single number. 03:55.570 --> 04:03.380 So this is another use case of anonymous functions, where you pass them to functions that work with 04:03.410 --> 04:09.920 arrays or maybe strings, so that you can perform some operation in place. 04:09.920 --> 04:18.800 And it wouldn't make a lot of sense to create a separate named function if what you are going to do 04:18.830 --> 04:23.750 will be applied only in one specific instance, like in here. 04:26.390 --> 04:26.720 Okay. 04:26.720 --> 04:28.190 So now another thing. 04:28.190 --> 04:36.560 So accessing variables in your anonymous functions that are outside the anonymous function itself. 04:36.800 --> 04:40.520 For an example let's copy this fragment. 04:41.060 --> 04:46.790 And here I don't want to actually say hello all the time. 04:46.790 --> 04:54.110 I'd like to use a message that is not passed as an argument to this anonymous function. 04:54.110 --> 04:55.340 Instead. 04:55.340 --> 05:00.470 That's just a variable defined outside this anonymous function. 05:00.470 --> 05:01.520 So it can be. 05:01.550 --> 05:02.570 Hello. 05:02.600 --> 05:05.510 Maybe I'd like to change it to by. 05:08.270 --> 05:08.900 Like this. 05:08.900 --> 05:11.210 Maybe let's also call this variable. 05:11.210 --> 05:12.260 Otherwise. 05:12.260 --> 05:19.670 Um maybe greet two didn't have any better idea. 05:19.670 --> 05:21.590 Anyway, let's run that. 05:21.590 --> 05:31.640 So PHP and PHP and we've got a warning that we are accessing an undefined variable message. 05:31.670 --> 05:34.880 Yet here we can see it is defined. 05:34.970 --> 05:42.950 So the thing with anonymous functions is that they don't have access to the variables defined outside. 05:42.980 --> 05:45.980 That's just a thing to access them. 05:45.980 --> 05:51.620 Well it's possible you can access the outside variables in your anonymous functions. 05:51.620 --> 05:59.790 When you also add this use statement after a function, and here you list the variables you'd like to 05:59.790 --> 06:03.300 be made available to your anonymous function. 06:03.660 --> 06:12.210 So after I define this, that I want this message variable to also exist in the context of this anonymous 06:12.210 --> 06:13.560 function. 06:13.680 --> 06:16.140 This should now work. 06:16.140 --> 06:19.530 And it does right. 06:20.790 --> 06:23.640 Now let's also think about this variable. 06:23.640 --> 06:26.550 So as the name suggests variable. 06:26.550 --> 06:28.890 It's something that can change. 06:28.890 --> 06:32.580 So you can change the value that variable holds. 06:32.580 --> 06:40.380 So can we change this variable the message that we get access to inside this function. 06:41.100 --> 06:42.480 Let's try that. 06:42.480 --> 06:46.290 Maybe I can use the original value. 06:46.320 --> 06:51.810 Concatenate that with an exclamation mark first and only then use it. 06:51.810 --> 06:56.230 So let me run this anon fbx file. 06:56.320 --> 07:06.340 As we see we had the exclamation mark, but after we have called this function, let's echo the message 07:06.370 --> 07:10.030 and let's see if its value has changed. 07:13.000 --> 07:15.340 Okay, let's run it again. 07:16.960 --> 07:25.210 So what happened here is we've modified the message, and this was reflected in whatever was returned 07:25.210 --> 07:27.220 from this anonymous function. 07:27.220 --> 07:34.540 But the original message variable defined here didn't changed and contains the original value, the 07:34.540 --> 07:37.150 original text that was set here. 07:37.150 --> 07:46.600 So that's the thing with using the external variables in anonymous functions, the copy of this variable 07:46.600 --> 07:51.490 is created that only exists in the context of this function. 07:51.850 --> 07:56.470 So to actually be able to change the value of this variable. 07:56.470 --> 07:57.610 If you would want that. 07:57.610 --> 08:04.030 Obviously you need to pass this variable by reference using this end sign. 08:04.090 --> 08:05.530 And then. 08:07.870 --> 08:12.520 The change would also be made in the original variable. 08:13.420 --> 08:18.130 So at this point the reference might be a foreign concept to you. 08:18.130 --> 08:21.010 And I haven't explained it yet. 08:21.040 --> 08:27.820 So now that we have learned enough about basic data types and functions, I think we should go back 08:27.820 --> 08:36.850 to the variables and talk about the variables scope, because having to use this external variable is 08:36.850 --> 08:45.790 the direct results of variables existing in certain scopes, and also passing by value and passing by 08:45.790 --> 08:49.900 reference is something I would have to explain. 08:50.080 --> 08:52.450 Let's talk about that next.