WEBVTT 00:00.560 --> 00:05.900 Okay, so it's time to learn about the special data type of null in PHP. 00:05.930 --> 00:14.810 That's very interesting data type, because it means that something is empty or it actually means nothing, 00:14.810 --> 00:22.970 and nothing can be associated to a variable and you can compare something to nothing. 00:23.000 --> 00:31.010 So let's see more examples, because in this case, we really need to see all the examples to understand 00:31.010 --> 00:34.100 the usefulness of the null data type. 00:34.130 --> 00:40.190 Let's start by creating a null PHP file and adding a PHP tag. 00:40.220 --> 00:45.260 Now let's start with var dumping a couple of things. 00:45.650 --> 00:51.710 So we're gonna compare null to different data types to values that look empty. 00:52.130 --> 00:58.460 First let's compare and keep in mind I'm using the comparison operator. 00:58.490 --> 01:01.100 Not strict comparison operator. 01:01.100 --> 01:03.560 So it ignores the data types. 01:03.560 --> 01:06.270 So first let's compare null to null. 01:06.300 --> 01:11.790 Then let's see if null is anything similar to false. 01:11.790 --> 01:15.210 Then let's compare null to zero. 01:15.810 --> 01:19.440 Then let's compare null to empty string. 01:19.740 --> 01:23.370 Next up, let's compare it to empty array. 01:23.460 --> 01:25.620 Um that was assignment. 01:25.650 --> 01:26.550 Let me fix that. 01:26.580 --> 01:28.890 Next up what else can we do. 01:28.890 --> 01:30.960 Well maybe that's enough. 01:31.590 --> 01:39.000 Now let's run PHP null PHP and we've got well basically five times. 01:39.000 --> 01:39.720 True. 01:39.750 --> 01:49.110 So the conclusion here is that PHP thinks that null or false or zero or empty string or empty array. 01:49.140 --> 01:50.610 This is nothing. 01:50.610 --> 01:52.650 This is empty. 01:52.920 --> 01:53.400 Okay. 01:53.400 --> 01:55.590 Now let's see another example. 01:55.590 --> 02:01.980 Let me add a non-existing variable and let's see what PHP will return for that. 02:01.980 --> 02:07.410 So other than warning we see that it has returned null. 02:07.410 --> 02:15.210 So if the variable doesn't exist, PHP returns nothing for it, which is null essentially. 02:15.210 --> 02:24.990 So null is also used to tell you that there is nothing to be returned, or that something contains nothing. 02:25.020 --> 02:27.390 This is what null means. 02:28.770 --> 02:36.060 Now it's also fine to just directly assign null to a variable or pass it around. 02:36.090 --> 02:43.050 If we run that again, the warning is gone, but the variable still contains the value null. 02:45.180 --> 02:50.370 Now next up in PHP you can check if a certain variable is defined. 02:50.400 --> 02:54.870 So to the var dump list let me add the function call. 02:54.870 --> 02:56.610 This function is called is set. 02:56.610 --> 02:59.910 And then you just pass a variable that you want to verify. 02:59.940 --> 03:03.990 Maybe DCA we know it doesn't exist. 03:03.990 --> 03:06.900 So let's run the script now. 03:08.190 --> 03:09.990 Okay so it returned false. 03:09.990 --> 03:10.800 It doesn't exist. 03:10.830 --> 03:13.600 We can see that we haven't defined this variable. 03:13.630 --> 03:19.780 So what happens if I check for the ABC variable that contains null? 03:20.140 --> 03:21.280 Let's run that. 03:22.090 --> 03:22.600 Hmm. 03:22.990 --> 03:30.910 So maybe this isn't super intuitive, but this is just one of the things in PHP that you would have 03:30.910 --> 03:31.990 to remember. 03:32.260 --> 03:35.260 So that's another I would say special case. 03:35.290 --> 03:42.550 I can say that this variable exists, but since its value is null is set returns false. 03:44.590 --> 03:48.670 Now you can also check a value for explicitly bank null. 03:48.700 --> 03:51.940 The reason is null function. 03:53.050 --> 03:59.710 And if I run ABC, I also get true because well this indeed is null. 04:01.180 --> 04:09.370 Next up, sometimes when there is a possibility that something is null, you might want to have an alternative 04:09.370 --> 04:11.140 or a default value. 04:13.420 --> 04:21.250 So let me have this DB variable And I'd like to assign ABC, but ABC can be null and we actually see 04:21.250 --> 04:22.480 that it's null. 04:22.480 --> 04:31.720 So then we can use a null coalescing operator to question marks and provide a default. 04:34.240 --> 04:39.940 So the way it works is the ABC value would be assigned to DB variable. 04:39.940 --> 04:41.590 If ABC is not null. 04:41.590 --> 04:45.190 If it's null, then the value on the right which is default. 04:45.220 --> 04:46.840 Let's output that. 04:47.620 --> 04:49.540 Then we have db. 04:50.440 --> 04:57.670 Now let's run the script again and it contains the default value because well this is how the null coalescing 04:57.670 --> 04:58.840 operator works. 05:00.640 --> 05:04.540 Next up let's see an example with a function parameter. 05:05.440 --> 05:09.340 So I will have a grid function that we've used before. 05:09.340 --> 05:12.760 And I expect the name to be a string. 05:12.790 --> 05:17.110 What if someone would not provide a value for the name? 05:17.110 --> 05:25.670 Well currently that's not possible, especially if we would do declare strict types. 05:28.040 --> 05:33.710 Equals one which requires us to respect the types strictly. 05:35.180 --> 05:37.100 So let me implement this function. 05:37.100 --> 05:45.590 So I would like to say hello and then concatenate that with the name. 05:48.110 --> 05:50.450 And maybe with an exclamation mark. 05:50.480 --> 05:54.830 And currently you have to pass something to it. 05:55.160 --> 05:57.860 So you have to pass let's say a lease. 05:57.860 --> 06:04.220 And it's not possible to not pass anything or pass null. 06:04.220 --> 06:09.410 So if I run it now, there will be a fatal error. 06:09.740 --> 06:17.060 So you can make parameters nullable if they are typed by adding a question mark before the type. 06:18.050 --> 06:23.930 So now you still have to provide the parameter value but it can be null. 06:29.330 --> 06:36.050 So this just produces text like this which is not ideal. 06:36.080 --> 06:38.120 Maybe let's add a new line here. 06:38.120 --> 06:40.670 So it is clearly visible. 06:40.850 --> 06:44.150 We just got an empty placeholder here. 06:44.150 --> 06:52.370 And again for such cases we can use the null coalescing operator and add the default, which would be 06:52.370 --> 06:57.380 stranger, which would be displayed if the name is not provided. 06:59.690 --> 07:06.470 Now by the way, since I've explained this exit function, another interesting PHP function that you 07:06.470 --> 07:09.560 actually might use often is empty. 07:09.590 --> 07:14.000 So empty will just return true for all these cases. 07:14.000 --> 07:22.250 If something is null, if it's false, if it's zero, if it is an empty string or an empty array. 07:22.700 --> 07:24.860 So let's just try one example. 07:24.860 --> 07:30.720 You can try more on your own, But that's a function to remember. 07:30.720 --> 07:33.570 So I think um, that's this one. 07:33.570 --> 07:36.720 So obviously empty array is empty. 07:37.320 --> 07:39.330 So that's a function to remember. 07:39.330 --> 07:46.770 This one is a function to remember is set and also is null is a handy function Rthy. 07:47.310 --> 07:57.810 Now another example is how can you remove the elements from the array that are equal to null. 07:57.840 --> 08:03.450 So this includes null itself false zero empty string empty array. 08:04.440 --> 08:13.560 So it's pretty important to also understand what would equal null because this is used across PHP language 08:13.560 --> 08:16.890 for different cases like the one you're going to see right now. 08:16.890 --> 08:20.220 So there is a function called array filter. 08:20.220 --> 08:21.780 It works with arrays. 08:21.810 --> 08:29.670 Now you can provide an anonymous function to it to process individual array elements the way you like, 08:29.670 --> 08:37.650 but by default it will just compare every single value to null, and if it is null or. 08:37.680 --> 08:41.760 It equals null when it is not strictly compared compared. 08:41.760 --> 08:47.100 So ignoring the type like an empty string or empty array. 08:47.100 --> 08:49.500 And then let's add a real number. 08:49.500 --> 08:53.700 It will remove all those elements from the resulting array. 08:53.700 --> 09:00.210 So if I run this right now you see that we only got two elements left. 09:00.240 --> 09:02.790 That's this number and that number. 09:02.790 --> 09:04.680 Everything else is gone. 09:04.680 --> 09:14.820 So that's also something I will repeat again that you should remember about those equalities. 09:15.360 --> 09:17.130 That null is also false. 09:17.130 --> 09:21.000 And if you compare those values this will return true. 09:22.680 --> 09:24.870 So there is always something more. 09:24.870 --> 09:30.030 And I can also tell you a little bit about null with objects. 09:30.030 --> 09:35.250 But we haven't talked about objects yet so I think that's enough for now.