WEBVTT 00:00.620 --> 00:05.090 So next up let's cover the references in terms of functions. 00:05.330 --> 00:11.900 So with functions the default behavior is always to pass the value by value. 00:11.930 --> 00:20.840 This means that like in this example I would like to pass the some var variable to my function and by 00:20.840 --> 00:23.000 default it's passed by value. 00:23.030 --> 00:29.990 This means that a copy of this variable is created inside the function and the value is copied. 00:30.020 --> 00:39.350 So if I perform some operations on by copy argument, I am modifying my local copy of that variable 00:39.350 --> 00:41.180 inside the function. 00:41.180 --> 00:44.570 The original variable is unaffected. 00:45.320 --> 00:51.860 Now if you pass by reference so you add this end sign before the argument. 00:52.220 --> 00:53.630 It's different. 00:53.630 --> 00:59.300 Then as you see, the color is the same, which means we are working on exactly the same variable. 00:59.330 --> 01:10.750 So other var passed to a function and then multiply it like this will modify this original variable 01:10.780 --> 01:15.880 because by ref in this case is just a reference, just an alias. 01:18.190 --> 01:21.100 Now let's define the value that we'd like to modify. 01:21.100 --> 01:28.480 Let's just call it original, and let's just vardump the value of original. 01:28.990 --> 01:33.850 After we call this function, this will be double value. 01:33.850 --> 01:37.420 And I'm passing this original variable. 01:37.450 --> 01:38.830 Let's just run that. 01:38.860 --> 01:40.360 That's by ref php. 01:41.020 --> 01:48.970 So the value of this original variable is five, which means it was unchanged because this function 01:49.180 --> 01:55.060 creates a copy of this variable that only exists in the context of this function. 01:55.060 --> 02:03.080 Thus, even modifying the argument like that does not really Modify the value that was passed when you 02:03.110 --> 02:04.370 call this function. 02:04.400 --> 02:09.230 Now it's another story when you pass by reference by adding this end sign. 02:11.330 --> 02:13.040 Let me run that again. 02:13.340 --> 02:22.640 Now we see that var dumping this variable named original returns ten, which means that it was modified 02:22.640 --> 02:24.080 by running this function. 02:24.080 --> 02:26.900 This is what passing by reference is. 02:28.010 --> 02:33.590 Now if you are wondering what's the use case of passing by reference? 02:33.740 --> 02:42.050 Again, I'd like to stress to not try to use this as a performance optimization unless you have reasons 02:42.050 --> 02:49.520 first, and you can only have reasons if you have tested the code, and you have the raw data showing 02:49.520 --> 02:55.040 you that the code is much faster or much more memory efficient. 02:55.100 --> 02:58.610 So such experiments make sense. 02:58.610 --> 03:01.120 If you have some heavy usage. 03:01.120 --> 03:05.830 Let's say you've got a lot of visitors to your application or website. 03:05.860 --> 03:13.420 You are doing some expensive calculations and you've done the experiments and see the data. 03:13.450 --> 03:21.220 Otherwise, you might be surprised that using references might be slower or use more memory. 03:21.550 --> 03:25.300 Again, don't use this for performance reasons. 03:25.330 --> 03:34.600 Now, one of the use cases of references in functions or passing by reference might be that it basically 03:34.600 --> 03:37.390 lets you actually modify a couple of values. 03:37.780 --> 03:41.890 Otherwise, with functions you can only return one value. 03:42.100 --> 03:51.040 And that's the case where you can pass, let's say three five parameters and modify them all instead 03:51.040 --> 03:53.830 of just being able to return one value. 03:54.400 --> 04:01.610 Now also keep in mind that just because something can be done doesn't mean that it should be done. 04:01.670 --> 04:11.060 So I personally am not a big fan of this pattern of trying to modify multiple values by passing them 04:11.060 --> 04:12.350 by reference. 04:12.470 --> 04:19.670 I don't think that this is very intuitive and I would do this otherwise. 04:19.670 --> 04:26.090 I would either use arrays to return multiple values or maybe objects. 04:26.120 --> 04:32.150 Now, we haven't talked about objects yet, but just so you know that this is possible. 04:32.150 --> 04:39.170 You can pass values by reference, but typically you just need to have a very good reason to explain 04:39.170 --> 04:39.710 that. 04:40.010 --> 04:46.250 And you just need to be aware and remember that PHP is optimizing a lot. 04:46.250 --> 04:55.460 So if you haven't run any measurements, then probably you shouldn't be trying to optimize and just 04:55.460 --> 04:58.070 stick to the default PHP behavior. 04:58.070 --> 04:59.780 And pass by value.