WEBVTT 00:00.050 --> 00:05.930 Next up, let's talk about the control structures, starting with the if statement. 00:05.960 --> 00:12.680 So as the name suggests, the control structures are used to control the flow of the program. 00:12.680 --> 00:21.740 And in the case of the if statement, you just conditionally run some statements if the expression that 00:21.740 --> 00:24.440 is being evaluated is true. 00:24.470 --> 00:33.920 Now you can also provide alternative cases using else if you can check for alternative conditions. 00:33.920 --> 00:43.820 If this first condition was false, and you can add as many as those alternative paths as you need, 00:43.820 --> 00:52.670 and only one of those will run and they will be checked until there is no other alternative condition. 00:52.670 --> 01:01.870 And optionally you can also add an else statement which will be run if none of those above conditions 01:01.870 --> 01:03.760 evaluated to true. 01:04.360 --> 01:10.210 As a quick reminder, the expression is something that always returns a value. 01:10.360 --> 01:14.800 That's what differentiates the expression from statement. 01:14.830 --> 01:21.850 Statement can be an expression, but it can also be a control structure like the if statement, which 01:21.880 --> 01:26.080 in this case means that if statements can be nested. 01:26.110 --> 01:30.070 Okay, let's do some practical exercises now. 01:30.760 --> 01:31.000 Okay. 01:31.030 --> 01:35.560 So let's jump into the code editor and create a new file. 01:35.590 --> 01:41.470 I'm going to call it FP as that's the topic of this video. 01:41.500 --> 01:43.090 Let me add a PHP tag. 01:43.090 --> 01:46.930 And immediately let's start with the first example. 01:46.930 --> 01:50.290 So for that I'm going to just declare a variable. 01:50.410 --> 01:53.560 Let's assign the value of ten to it. 01:53.560 --> 01:56.710 And let's write a simple if statement. 01:56.710 --> 02:03.240 So it starts with the if keyword, then we've got parentheses that's mandatory. 02:03.240 --> 02:10.020 And inside it we need to add an expression that will evaluate to boolean value. 02:11.370 --> 02:19.500 So the condition inside the parentheses must evaluate to a Boolean value because we essentially have 02:19.530 --> 02:20.910 two choices. 02:20.910 --> 02:29.250 So either this conditional statement that depends on this condition inside parentheses will run or it 02:29.250 --> 02:29.880 won't. 02:30.090 --> 02:32.910 And that's why it needs to be a boolean. 02:32.940 --> 02:35.490 Now I'm adding a curly braces. 02:35.490 --> 02:37.980 So first let me add a condition here. 02:37.980 --> 02:42.750 I'm gonna just check if x is bigger than five. 02:42.750 --> 02:46.830 So currently I think we can be sure that that's true. 02:46.830 --> 02:49.470 But that's the thing with variables. 02:49.470 --> 02:51.510 Variables can change. 02:51.510 --> 02:55.380 And there might be a different value here that needs to be verified. 02:55.410 --> 03:01.400 Now I'm just going to say x is greater than five. 03:01.400 --> 03:06.140 And let me add a new line here and let's run it. 03:06.170 --> 03:07.280 That's BHP. 03:07.310 --> 03:08.270 If BHP. 03:08.300 --> 03:12.980 Now obviously in this case ten is greater than five. 03:13.250 --> 03:21.380 Most people prefer this convention of always using curly braces, but they are not always mandatory. 03:21.380 --> 03:30.440 So if you would only have one statement inside your if control structure, then you can skip the curly 03:30.440 --> 03:30.980 braces. 03:30.980 --> 03:32.660 So this is also fine. 03:32.660 --> 03:35.540 And I can confirm that by running this code. 03:36.470 --> 03:39.230 So I'm gonna use the curly braces everywhere. 03:39.230 --> 03:42.080 I think it is a good convention. 03:42.080 --> 03:48.590 It makes the code much more clear, especially if you have nested if statements. 03:49.730 --> 03:55.040 So this statement only runs if this condition is true. 03:55.040 --> 03:58.960 But if this condition is false, then nothing happens. 03:58.960 --> 04:03.610 So let's see another example where we're going to have some alternatives. 04:03.610 --> 04:10.540 And this is calculation of the grade for a student based on his score in points. 04:10.540 --> 04:15.610 So let's say the score is 85 out of 100 points possible. 04:15.610 --> 04:18.370 Now we need to give students the grade. 04:18.370 --> 04:21.070 So we check for the score. 04:21.100 --> 04:26.620 If it's more than 90 we're going to just echo a. 04:26.650 --> 04:30.190 Keep in mind this here is not one character. 04:30.220 --> 04:36.370 Those are actually two characters more than followed immediately by equality sign. 04:36.370 --> 04:38.860 It's just called a ligature. 04:38.860 --> 04:45.010 And this is how the text editor just renders that those are two characters. 04:45.100 --> 04:45.640 Okay. 04:45.670 --> 04:53.410 So now I want to provide an alternative, because we can expect that it's quite possible that a lot 04:53.440 --> 04:57.210 of people will have a score lower than 90. 04:57.210 --> 05:05.490 So in this case, I'm gonna check if maybe the score is more than or equal 80. 05:05.520 --> 05:09.270 And then I'm going to give it a B. 05:09.420 --> 05:13.560 So let me copy paste that two more times. 05:14.580 --> 05:19.590 So we've got different thresholds in here 7060. 05:19.710 --> 05:23.850 This results in C and this results in D. 05:24.030 --> 05:32.670 Now for all other cases when someone is below 60 there is no point in actually adding a specific condition 05:32.670 --> 05:33.450 for this. 05:33.450 --> 05:37.200 And in that cases we can just go with else. 05:37.200 --> 05:43.590 So for all the other cases then you're getting an F. 05:45.240 --> 05:51.540 So this might also cover a case when someone doesn't have a score, because maybe he just didn't show 05:51.540 --> 05:52.890 up for the exam. 05:52.890 --> 05:58.190 And then he gets F Okay, so now let's run it. 05:58.220 --> 06:09.920 We do PHP if PHP and in this case the score is B, if I change the score to, let's say 60 to be on 06:09.920 --> 06:13.190 the edge, this is D. 06:14.570 --> 06:14.870 Okay. 06:14.870 --> 06:17.060 So that was another example. 06:17.060 --> 06:21.710 Now let's see how can we use nested if statements. 06:24.050 --> 06:30.320 So next up let's define a variable that will be just called num as a number. 06:30.320 --> 06:37.190 And we'll try to say something about the number that is currently inside the variable. 06:38.210 --> 06:43.760 So the first condition here is checking if the number is something positive. 06:43.760 --> 06:46.010 So something more than zero. 06:47.600 --> 06:56.830 And if that's not the case we just echo non A positive number. 06:58.930 --> 07:04.630 But if it is positive, we're going to check if this is an even or an odd number. 07:06.010 --> 07:13.750 Now, the easy way to check if the number is even or odd is to use the modulo operator, which just 07:13.750 --> 07:18.730 gives you a remainder of division by two. 07:18.760 --> 07:25.990 So if in this case that is zero, then we know we have an even number. 07:26.830 --> 07:31.420 So we can say a positive even number. 07:32.470 --> 07:42.280 And in the other case we just used else and we say echo positive odd number. 07:42.940 --> 07:50.410 Now let me add a new line character before every single one of those strings and after. 07:50.410 --> 07:53.820 So that we just have a clear output. 07:53.820 --> 07:57.420 And now let's run this if script. 07:57.420 --> 08:01.620 So currently we've got a positive odd number. 08:02.190 --> 08:03.630 That's the case. 08:03.720 --> 08:07.890 Now let's rerun it again by changing the number to 14. 08:07.920 --> 08:10.020 That's a positive even number. 08:10.050 --> 08:11.340 Yes that's correct. 08:11.340 --> 08:17.010 And minus three this is a non positive number. 08:18.510 --> 08:25.740 You should know that in control structures which just have one statement inside their body. 08:25.740 --> 08:30.810 And the body is basically everything between the curly braces. 08:30.810 --> 08:31.800 So that's a body. 08:31.800 --> 08:37.860 For example if there is only one statement inside you don't need to use curly braces. 08:37.860 --> 08:44.970 So now I can remove all of those curly braces here and everything would still work fine. 08:45.810 --> 08:54.740 Now most people would prefer the convention to always add curly braces, But just so you know, it is 08:54.740 --> 08:55.880 just a convention. 08:55.880 --> 08:59.240 And this code here is totally fine. 08:59.240 --> 09:05.480 And it would work and I can run it and everything is fine. 09:05.480 --> 09:12.470 So just so you know, this nested if statement is basically considered bank one statement. 09:12.470 --> 09:16.310 So I'm going to bring it back to using curly braces. 09:17.480 --> 09:21.590 But well you should know about all the possibilities. 09:21.590 --> 09:30.050 And another benefit of using the curly braces is that I get this highlighting in the code editor of 09:30.050 --> 09:31.760 the matching curly braces. 09:31.760 --> 09:39.290 This really helps if you have bigger blocks of code that might be longer, and might really be longer 09:39.290 --> 09:42.320 than what you currently see on the screen. 09:43.520 --> 09:49.250 Okay, so let's have a final example with the username and password. 09:49.250 --> 09:51.170 So let's define two variables. 09:51.170 --> 09:59.440 The username, which would be admin, and the password which can be just password one two, three. 09:59.680 --> 10:08.860 Now we're gonna add an if statement and we'll check if the username is specifically admin. 10:09.430 --> 10:16.840 And we're going to add a logical operator because we also need to make sure that both are true. 10:16.840 --> 10:23.020 So username is exactly admin and that also password. 10:23.050 --> 10:24.190 That's why we use this. 10:24.220 --> 10:30.610 And operator that password is exactly password 123. 10:33.250 --> 10:37.450 So if that's fine we just say success. 10:37.450 --> 10:41.140 And otherwise you can say failure. 10:41.530 --> 10:43.870 I'm missing the echo statement here. 10:43.900 --> 10:52.440 Now just keep in mind that in real applications you will have the users and the passwords stored inside 10:52.440 --> 10:56.850 the database, and they would not be stored as plain text. 10:56.850 --> 10:59.220 They will be encoded. 10:59.250 --> 11:03.060 So this here is just a simple example. 11:03.060 --> 11:06.990 So we can showcase more examples with the if statements. 11:07.020 --> 11:09.810 Now let's run that in the terminal. 11:09.810 --> 11:11.580 And we have a success. 11:11.580 --> 11:18.750 And if I would change this password even slightly we should have a failure. 11:18.870 --> 11:19.470 Okay. 11:19.500 --> 11:21.030 So let's summarize. 11:21.030 --> 11:26.640 So we've seen some new operators like this logical operator. 11:26.640 --> 11:36.540 We've had examples of the if statements by having the else alternatives and also else if alternatives. 11:36.540 --> 11:39.960 We've used the nested if statements. 11:39.960 --> 11:47.730 And also we learned that the control structures, if there is just one statement inside their body, 11:47.760 --> 11:50.250 you can skip the curly braces.