Beginner's Guide to PHP and Databases

Getting Started Guide to PHP and Databases

With the development of the Internet, PHP has been widely used as a powerful programming language. In Internet applications, databases are also a key component. Therefore, learning PHP and databases and mastering their basic knowledge has become a required course for many programmers. This article will provide you with an introductory guide to PHP and databases to help beginners get started easily.

1. Overview of PHP language

PHP is a server-side scripting language. Through PHP, we can generate dynamic web content, dynamically process forms, create, open, read, write, close files on the server, send and receive cookies, etc. PHP provides extensive support for a variety of databases and is widely used in the field of web development. The latest version of PHP is currently PHP 8.0.

2. Install PHP

Before learning PHP, we need to install PHP first. The following are the steps to install PHP:

1. Visit the official website: https://www.php.net/downloads.php

2. Select the corresponding PHP version to download, here we use PHP 8.0 .0 for example.

3. Extract the downloaded file to a local folder.

4. Find the php.ini-development file in the unzipped folder, copy it and rename it to php.ini.

5. Find the following two lines of code in the php.ini file and remove the semicolon (;):

extension=mysqli
extension=pdo_mysql

6. Add the path to the unzipped folder to the environment variable so that the PHP file can be executed in any folder.

3. PHP language basics

1. Output statement

One of the most commonly used statements in PHP is the echo statement, which can output text, variables, tags, etc. to the web page.

For example:

<?php

echo "Hello World!";

?>

2. Variables

When creating variables in PHP, you need to use the $ symbol to distinguish tags and variable names.

For example:

$number = 5;

echo $number;

3. Conditional statements

There are if, else if, else and other conditional statements in PHP, which are used to execute different code segments according to different conditions. .

For example:

$score = 90;

if($score >= 90) {
    echo "优秀";
} else if($score >= 60) {
    echo "及格";
} else {
    echo "不及格";
}

4. Database Basics

1. What is a database

A database is a software system used to store and manage data. Through the database, we can easily store and access large amounts of data, and can reduce the risks of data duplication and data inconsistency.

2. Relational databases and non-relational databases

Commonly used database systems mainly include relational databases and non-relational databases. Relational databases store data in relationships in the form of tables, and are operated by relational algebra and SQL language. Non-relational databases store data in the form of key-value pairs and use specific data structures for operations.

3.MySQL database

MySQL is currently one of the most popular open source relational database management systems. It is a client/server application written in C and C that can be used for web development, data warehousing, mobile applications, etc.

4. PHP connects to MySQL database

The following are the steps to connect to MySQL database:

1. Open the PHP file and add the following code at the beginning:

<?php

//定义连接参数
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

//创建连接
$conn = new mysqli($servername, $username, $password, $dbname);

//检查连接是否成功
if($conn->connect_error) {
    die("连接失败：" . $conn->connect_error);
} 
echo "连接成功！";
?>

2. Connection parameter explanation:

$servername: MySQL server name
$username: MySQL user name
$password: MySQL password
$dbname: Name of the MySQL database to be connected

$conn = new mysqli($servername, $username, $password, $dbname): Create a connection

3. Operate the MySQL database

After the connection is successful, we can The MySQL database is operated. The following is a code example for adding, deleting, modifying, and querying operations on the MySQL database:

//插入数据
$sql = "INSERT INTO MyGuests (firstname, lastname, email) VALUES ('John', 'Doe', 'john@example.com')";

if($conn->query($sql) === TRUE) {
    echo "新记录插入成功！";
} else {
    echo "错误：" . $sql . "<br>" . $conn->error;
}

//更新数据
$sql = "UPDATE MyGuests SET lastname='Doe' WHERE id=2";

if($conn->query($sql) === TRUE) {
    echo "记录更新成功！";
} else {
    echo "错误：" . $sql . "<br>" . $conn->error;
}

//删除数据
$sql = "DELETE FROM MyGuests WHERE id=3";

if($conn->query($sql) === TRUE) {
    echo "记录删除成功！";
} else {
    echo "错误：" . $sql . "<br>" . $conn->error;
}

//查询数据
$sql = "SELECT id, firstname, lastname FROM MyGuests";
$result = $conn->query($sql);

if($result->num_rows > 0) {
    //输出数据
    while($row = $result->fetch_assoc()) {
        echo "id: " . $row["id"]. " - Name: " . $row["firstname"]. " " . $row["lastname"]. "<br>";
    }
} else {
    echo "0 结果";
}

The above code can implement the adding, deleting, modifying, and querying operations on the MySQL database and output the results.

5. Conclusion

This article introduces the basic knowledge and operation methods of getting started with PHP and database. By studying this article, beginners can master the basic knowledge of PHP and databases, and can add, delete, modify, and query data by connecting to the MySQL database. I hope this article will be helpful to everyone’s study!

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