[php learning] Notes on the first chapter of PHP introductory classic, PHP Chapter 1_PHP tutorial

[php learning] PHP introductory classic chapter 1 notes, php chapter 1

Chapter 1:

php online manual: http://php.net/manual/zh/index.php

Before starting to learn PHP, let’s first look at what knowledge a qualified PHP programmer should have in the future. Here are just some summaries of the author. I hope it will be helpful to readers in their next studies.

In a broad sense, it is not enough for PHP programmers to only master PHP. They need to master more knowledge in the process of learning PHP, so that they can develop better and more complete software. In the process of setting up the front-end page, you need to master HTML, DIV, CSS, Javascript, etc.; in terms of program security, you need to master basic server configuration knowledge, security filtering permissions, etc.; in terms of program optimization and performance, you need to master the basic knowledge and optimization of the database, etc. .

Before starting to learn the knowledge in this book, you should make the following preparations.
❑Have enough confidence and preparation time (many losers give up halfway because they don’t have time).
❑A little mathematical foundation (relatively less used, PHP focuses more on logic programming).
❑A little basic knowledge of English (just know 26 letters).
❑A little bit of network basics (just understand some basic network terms, such as email, HTTP, login, etc.).

1. Simple [Explanation] During the running of the PHP program, the respective functions of the PHP preprocessor, web server and database are briefly described, and the workflow of the PHP program is briefly described

Function of php preprocessor: asp PHP .net web language is the same, through its own calculation mechanism and database query. The results are generated on the server and displayed to the client through HTML.

Function of the web server: The web server is used to receive HTTP requests and respond to this request (such as operating database data according to the client's request), usually in WEB development If the client initiates a request to the server, there must be a WEB server, otherwise no one will accept the request.

Function of database:A database is a set of data organized by a computer, stored in one or more files, and the software that manages this database is called It is a database management system.

Has the following functions:
(1) Data definition function. DBMS provides corresponding data languages ​​to define (DDL) database structures, which describe the database framework and are stored in the data dictionary.
(2) Data access function. DBMS provides data manipulation language (DML) to implement basic access operations on database data: retrieval, insertion, modification and deletion.
(3) Database operation management function. DBMS provides data control functions, that is, data security, integrity and concurrency control to effectively control and manage database operations to ensure that the data is correct and effective.
(4) Database establishment and maintenance functions. Including the loading of initial data of the database, database dump, recovery, reorganization, system performance monitoring, analysis and other functions.
(5) Database transmission. DBMS provides the transmission of processing data and realizes communication between user programs and DBMS, which is usually completed in coordination with the operating system.

Workflow of PHP program: PHP is a server-side programming language. The programming statements are similar to C language. Your program logic is translated into HTML hypertext tags that the browser can recognize. Language, displayed in the client browser.

What is the process for a web server to run the php script language?

The web server is used to receive HTTP requests and respond to this request (such as operating database data according to the client's request). Usually in WEB development, if the client initiates a request to the server, then there must be a WEB server, otherwise no one will accept this request. In the early days of WEB development, CGI was used to handle client requests. At that time, there was no language such as PHP designed specifically for WEB development, and it was not possible to separate HTML code and background logic code, so CGI programs The returned results usually contain some HTML code, and the browser receives the entire result and renders it. Later, after development, PHP became a WEB development language that can separate the front and back ends. The PHP code is only responsible for processing the background logic. A large amount of HTML code is placed in a static HTML file. The final rendering result of the browser is the HTML returned by the server. The comprehensive result of code plus JS code plus CSS code and PHP template output. In the early days, the web server was run using CGI as a bridge and then running the PHP scripting language.

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