WEBVTT 00:00.440 --> 00:08.930 So in the previous video, I've mentioned the concept of references, and also we had to use a variable 00:08.930 --> 00:14.600 from outside the function to even be able to read the value of that variable. 00:14.600 --> 00:23.540 And this introduces two separate concepts the variable scope and the references. 00:23.630 --> 00:27.050 So in this video we're gonna talk about references. 00:27.050 --> 00:34.310 So I've kept those two topics for later on purpose because they might be complex. 00:34.310 --> 00:37.340 And we had to explain functions first. 00:37.340 --> 00:40.370 So now's the time to understand both. 00:40.400 --> 00:42.590 Let's start with references. 00:42.590 --> 00:49.400 We're gonna have a theoretical short explanation first and then we'll jump to the code examples. 00:50.240 --> 00:52.130 So let's use an example. 00:52.160 --> 00:57.290 Imagine you have this person variable to which you assign a string John. 00:57.470 --> 00:58.970 This is simple. 00:59.180 --> 01:05.960 And next you'd like the client variable that just be the same as the person. 01:05.960 --> 01:12.950 But in this case, we don't associate the value of the person variable to the client variable. 01:12.950 --> 01:17.870 Instead, this end sign creates a reference. 01:17.870 --> 01:24.860 So what reference means is that client is now an alliance to the person variable. 01:24.860 --> 01:34.100 And if you read the value of client or you set it, you are actually modifying the value of person variable. 01:34.280 --> 01:37.550 And those two are now connected. 01:37.550 --> 01:45.860 And that's because the client variable is essentially pointing to the same space in your computer memory 01:45.860 --> 01:50.330 or the server memory, which person variable does. 01:50.330 --> 01:54.140 So you are accessing the same space. 01:54.140 --> 01:58.430 So when you read the value of both variables they return. 01:58.430 --> 01:59.240 John. 01:59.480 --> 02:05.850 But what's more important when you change the value of either person or client. 02:05.880 --> 02:13.560 Both will change if I change the value of person by reassigning it to, let's say, Bobby. 02:13.590 --> 02:17.130 Then when I read client, it will return Bobby. 02:17.190 --> 02:25.710 If, on the other hand, I'm gonna change the client value to Richard, then if I read the person variable, 02:25.710 --> 02:27.390 it will return. 02:27.390 --> 02:28.500 Richard. 02:28.530 --> 02:33.420 So they are now both pointing to exactly the same space. 02:33.450 --> 02:36.150 And now let's see some examples. 02:38.790 --> 02:43.710 So in the main folder this time let's create a refs file. 02:43.740 --> 02:45.630 Refs peachpie is fine. 02:45.960 --> 02:48.240 And a PHP tag. 02:48.240 --> 02:51.360 And well let's use this example. 02:51.360 --> 02:55.740 So we had a person and this was John. 02:56.430 --> 02:59.400 Now let's create a client variable. 02:59.400 --> 03:02.730 And that's a reference to person. 03:06.090 --> 03:12.230 Now let's vardump the value of both the person and the client. 03:14.060 --> 03:18.890 Now I'm going to change the value of client to Robert. 03:19.730 --> 03:22.520 And let's also vardump both. 03:22.520 --> 03:30.890 And then let's change the value of person to Harry and Vardump both. 03:30.980 --> 03:32.570 Now let's run this. 03:32.570 --> 03:34.310 So we do PHP refs. 03:34.550 --> 03:35.000 PHP. 03:36.200 --> 03:42.140 So we are starting with both pointing to the value of John by creating this reference. 03:42.140 --> 03:44.390 And then you see the pattern. 03:44.420 --> 03:46.490 I've changed the client. 03:46.490 --> 03:51.590 So the one pointing to the original value and both show Robert. 03:52.400 --> 04:00.710 If I change the original person variable, the client is also pointing to the new value because they 04:00.710 --> 04:04.880 are pointing to the exactly same space in memory. 04:04.880 --> 04:08.030 So they have to have the same value. 04:10.300 --> 04:16.720 Now before you jump into your code and pass everything by reference and use references everywhere, 04:16.720 --> 04:25.990 I'd like to warn you not to do that, and just don't try to use the references for optimizations, because 04:26.200 --> 04:34.660 PHP is already pretty optimized, and using references is actually more dangerous because you can accidentally 04:34.660 --> 04:36.580 modify the value. 04:36.610 --> 04:44.860 So before you jump to any kind of optimizations, it's essential to first test your ideas. 04:44.860 --> 04:51.430 Just see how much faster your code is or how much less memory it's using. 04:51.460 --> 04:55.930 So you should never default to using references. 04:55.930 --> 05:03.310 Thinking about potential optimizations because you might be surprised that sometimes or even often the 05:03.310 --> 05:11.080 code without references, which are some additional overhead, might be faster and more memory efficient.