WEBVTT 00:01.460 --> 00:05.930 PHP alone is not enough to create a dynamic website. 00:06.020 --> 00:09.560 You actually need a web server software. 00:09.560 --> 00:18.470 So here let's have a high level overview of where does exactly PHP come into play, and what are the 00:18.470 --> 00:22.400 other things that are required to have a working website. 00:23.780 --> 00:29.540 Now let me zoom in a little bit so we can clearly see every step along the way. 00:30.020 --> 00:32.900 Everything starts with a client. 00:32.930 --> 00:41.090 Now client can just be a person browsing the website through the web browser, or just accessing your 00:41.090 --> 00:43.580 server application in any other way. 00:43.580 --> 00:46.730 And the client makes a request. 00:46.730 --> 00:51.320 So PHP alone can't handle the requests for that. 00:51.320 --> 00:53.840 You need some kind of a web server. 00:53.870 --> 00:58.010 Typically, nginx is a popular choice. 00:58.040 --> 01:04.520 Other popular choices is for example, the Apache web server or caddy baths. 01:04.670 --> 01:14.620 So if the code of our application is written using PHP, this server software alone cannot run it. 01:14.650 --> 01:19.840 It needs to pass the PHP code to PHP itself. 01:19.840 --> 01:25.570 And the way to do that for web servers is the Fastcgi. 01:25.600 --> 01:35.770 Now this sounds complex, but the shortcut means fast common gateway interface, and that's just a protocol 01:35.770 --> 01:41.800 that web server software use to communicate with external programs. 01:41.830 --> 01:49.990 That's nothing specific to PHP, it's just a way web server software like nginx, but also Apache and 01:49.990 --> 01:58.450 others use to communicate with external programs, and PHP is one of those external programs. 01:59.260 --> 02:10.540 Next we've got something called PHP, FPM and this shortcut means PHP Fastcgi Process Manager. 02:10.540 --> 02:17.950 And that's just an implementation of this fast CGI protocol for PHP. 02:18.220 --> 02:28.870 And it manages a couple of processes called worker processes that can do something with the PHP code. 02:28.870 --> 02:37.690 So once the web server is passing the request on to PHP Process Manager, one of those worker processes 02:37.690 --> 02:47.080 can pick up the PHP code, and only then we get to this blue box where the PHP interpreter runs. 02:47.470 --> 02:50.560 So PHP is an interpreted language. 02:50.560 --> 02:55.150 This means that PHP code is not turned into a binary. 02:55.150 --> 02:59.170 It needs to be interpreted every single time. 02:59.200 --> 03:01.270 Only then it can be run. 03:01.270 --> 03:06.940 That differs, for example, from programs that you might have on your computer, whether Windows or 03:06.940 --> 03:15.330 Mac OS, which are compiled and you probably don't even know in which language they were created. 03:15.330 --> 03:17.730 So that's not the case with PHP. 03:18.120 --> 03:20.130 PHP is interpreted. 03:20.160 --> 03:28.890 Now let's try to quickly understand how does it happen and how can this process of PHP interpretation 03:28.920 --> 03:30.510 be optimized? 03:31.800 --> 03:36.390 Next up, let's try to quickly understand how the PHP interpreter works. 03:36.390 --> 03:43.680 So we just need to understand that we humans are able to comprehend complex structures. 03:43.680 --> 03:49.320 And this also includes code which typically can include complex operations. 03:49.320 --> 03:52.050 But that's not really the case with computers. 03:52.080 --> 03:59.160 Computers need to translate everything into simple list of operations that should be performed one by 03:59.160 --> 03:59.700 one. 03:59.700 --> 04:02.010 And that's the job of the interpreter. 04:02.010 --> 04:04.170 So it starts with a tokenizer. 04:04.170 --> 04:10.680 And I'm going to use a natural language that we all speak as an example, whether that's English, German 04:10.680 --> 04:12.000 or French. 04:12.390 --> 04:19.980 So when you take a look at the text in any of the languages, I mean English, German, you see some 04:19.980 --> 04:21.030 random letters? 04:21.030 --> 04:22.680 It might seem so at least. 04:22.680 --> 04:26.670 But if you look closer, then there are words. 04:26.670 --> 04:29.070 Words are separated by spaces. 04:29.070 --> 04:33.990 And that's what tokenizer is doing with the programming code. 04:33.990 --> 04:41.820 So tokenizer is changing just a group of characters into tokens. 04:41.820 --> 04:45.840 So it's like distinguishing words. 04:45.840 --> 04:48.120 And tokens can be keywords. 04:48.120 --> 04:53.100 Some special characters like parentheses or curly braces. 04:53.340 --> 04:57.810 So the first step is breaking the code into the tokens. 04:57.840 --> 04:59.970 Next we've got parser. 05:00.000 --> 05:08.010 The parser is creating something called abstract syntax tree, which is just a tree representation of 05:08.010 --> 05:11.040 your code flow and what should happen. 05:11.040 --> 05:18.630 And the third step is the actual compiler that creates this simple operations called opcodes. 05:18.630 --> 05:27.320 So only after we have those opcodes our PHP code is actually being run, so it's simple enough for computers 05:27.320 --> 05:28.850 to understand at this point. 05:28.850 --> 05:35.630 And it is being executed by the executor, which in PHP is just called Zend Engine. 05:35.660 --> 05:41.090 Now, as you might see here, this process can be further optimized. 05:41.090 --> 05:50.060 You can use something called Opcache, which is just a way to keep the compiled opcodes between subsequent 05:50.060 --> 05:53.780 requests inside this opcache. 05:53.810 --> 05:58.640 Now, keep in mind that everything I'm explaining here is quite complex. 05:58.640 --> 06:00.800 Compilers are hard. 06:00.800 --> 06:02.390 It's a complex problem. 06:02.390 --> 06:09.500 I am telling you this at this point so that you just know more or less how it all works. 06:09.980 --> 06:11.810 Yths. 06:12.500 --> 06:21.710 Finally, this executor is just running the PHP code that we were so painstakingly writing, and the 06:21.710 --> 06:29.420 executor is just interacting with all the external things like the database to fetch the data or store 06:29.450 --> 06:33.650 it as typically you will be using some kind of a database. 06:33.650 --> 06:41.270 Let's say even for a simple blog written using PHP, you might want to fetch those blog posts from the 06:41.270 --> 06:42.290 database. 06:43.040 --> 06:48.950 So you might also work with the file system, whether this is with images or some kind of documents, 06:48.950 --> 06:51.380 whatever your application will need. 06:51.380 --> 06:58.520 And then you should also know that the PHP functionality is extended by extensions. 06:58.520 --> 07:03.170 So extensions is not something that you or I would be creating. 07:03.200 --> 07:09.290 It's created by the community and typically it's written in the C language. 07:09.290 --> 07:17.930 So the idea behind extensions is that PHP language and runtime can be kept quite pure. 07:17.930 --> 07:25.880 And if there are any needs for PHP to work with any external technology, whether that's database or 07:25.880 --> 07:33.850 you need to handle image processing, then this functionality is built into Extensions. 07:34.030 --> 07:43.270 So PHP ships with a set of some popular, often used extensions by default, but if you require some 07:43.270 --> 07:49.900 additional functionality, then there might be extensions existing for that very purpose, which, as 07:49.900 --> 07:54.430 I've said, also lets PHP be kept clean. 07:57.340 --> 08:00.880 All right, so then we are just going back. 08:00.880 --> 08:10.240 So once the PHP interpreter will do its job by tokenizing, parsing, compiling and executing PHP code, 08:10.240 --> 08:13.540 then it will just get some output. 08:13.540 --> 08:17.410 That's typically an HTML page, but it can be anything. 08:17.440 --> 08:25.270 And then it will be returned back through the worker back to the web server, which then sends this 08:25.270 --> 08:30.910 as a response to the client, which typically, as I've said, is a web browser. 08:30.910 --> 08:37.360 So the person visiting your website or page will see the output that he wanted.