24.4.11 PHP and MySQL database

24.4.11.1 PHP MySQL extension

The functions for processing MySQL data in PHP are developed and provided as extensions of PHP. The following extensions have been developed so far.

■ Original MySQL extension

This is an extension function that was originally developed to access MySQL data in PHP. It was originally developed with the assumption that it will be applied only to systems prior to MySQL version 4.1.3. It can be applied to later versions, but it can not fully utilize the functions of the latest MySQL server, and it will be discarded in the future.

24.4 PHP Web Script Language

24.4.1 HTML and PHP

24.4.1.1 Needs for PHP

On the Internet, all web servers use HTML to receive a request from web browser which is client, and then deliver the necessary data accordingly to the web browser to express it as a general form that human can understand. HTML (Hyper-Text Markup Language) allows a web server to communicate with a web browser and send/receive data each other, and return the processing results back to people.

24.3.4 Simple HTML Web Page

24.3.4.1 Using Link to Other URL

Next is an example of linking a URL of another homepage to a specific sentence, and if clicking the sentence, the screen is switched to the specified URL.

24.3.3 Summary of HTML Syntax

24.3.3.1 HTML Overview

HTML (Hyper-Text Markup Language) is a basic language to define Internet web page. A web page consists of HTML document in the form of a tag, is transmitted via Internet, and expressed through a web browser. HTML is used to display a desired picture and text and to define function to perform a specified operation on a specific item when a web page is displayed to a user through a web browser.

24.3.2 Installing

24.3.2.1 Installing

When installing on Raspberry Pi, use the following command:

sudo apt-get install apache2

24.3 Apache web server

24.3.1 Web server and Apache

24.3.1.1 Web server

By installing a web site on the Internet, people can access the site through a web browser, view the data they want, and do other various necessary works.

A web server is required to install and operate such a web site. People send various client requests to a web site through a web browser. At this time, web server is the application to perform functions that receive the request from the client, interpret the contents, perform necessary processing, and then return the web page contents of the corresponding web site to the client.

24.2.5 Database SQL

24.2.5.1 Introduction of Database SQL

All relational databases use special instruction called SQL (Structured Query Language) to manage their internal data. By using SQL, you can define the type and content of data in the database, to enter data into the database, to modify the data entered, and to view the data entered.

The main functions of SQL that are necessary for database management are as follows: