Getting Started with PHP: PHP and SQL

PHP is a widely used server-side scripting language that can be used to create dynamic web pages and web applications. SQL is a language used to store, manage and retrieve data. This article will introduce the basics of PHP and SQL and how to use them together.

1. What is PHP?

The full name of PHP is "Hypertext Preprocessor", which is a scripting language that can be executed on the server. PHP was founded in 1994 by Rasmus Lerdorf to create a simple tool to track his personal traffic. Now, PHP has become a powerful development tool and is widely used in web development and application development.

PHP has very powerful functions, including processing forms, processing files, creating databases, managing sessions, etc. At the same time, PHP can also be easily integrated with other applications and databases.

2. What is SQL?

The full name of SQL is "Structured Query Language", which is a language used to store, manage and retrieve data. SQL was created by IBM's R.M. Boyce and Donald D. Chamberlin in the early 1970s and was initially used for querying relational databases. Now, SQL has become the standard language for relational databases.

SQL has very powerful functions, including creating tables, inserting data, querying data, updating data, etc. The SQL language is also very flexible and can be adapted to various types of database management systems.

3. How to use PHP and SQL together?

PHP can be integrated with various types of databases, including MySQL, Oracle, Microsoft SQL Server, etc. The following takes MySQL as an example to introduce how to use PHP and SQL together.

1. Connect to the MySQL database

To connect to the MySQL database, you need to use the mysqli extension of PHP. The following is a sample code to connect to a MySQL database:

<?php
$servername = "localhost";
$username = "username";
$password = "password";
$database = "database";

// 创建连接
$conn = mysqli_connect($servername, $username, $password, $database);

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

This code uses the mysqli_connect() function to connect to the MySQL database. Among them, $servername represents the server name, $username represents the user name, $password represents the password, and $database represents the name of the database to be connected. If the connection fails, the function will return false.

2. Execute SQL query

To execute SQL query, you need to use PHP's mysqli_query() function. The following is a sample code for querying data:

<?php
$sql = "SELECT id, name, email FROM users";
$result = mysqli_query($conn, $sql);

if (mysqli_num_rows($result) > 0) {
    // 输出数据
    while($row = mysqli_fetch_assoc($result)) {
        echo "id: " . $row["id"]. " - Name: " . $row["name"]. " - Email: " . $row["email"]. "<br>";
    }
} else {
    echo "0 结果";
}

mysqli_close($conn);
?>

This code uses the mysqli_query() function to execute a query statement, and uses the mysqli_fetch_assoc() function to obtain the results row by row. If the result is empty, "0 result" is output.

3. Insert data

To insert data, you need to use PHP’s mysqli_query() function. The following is a sample code for inserting data:

<?php
$sql = "INSERT INTO users (name, email, password) VALUES ('John Doe', 'johndoe@example.com', 'password123')";

if (mysqli_query($conn, $sql)) {
    echo "插入成功";
} else {
    echo "Error: " . $sql . "<br>" . mysqli_error($conn);
}

mysqli_close($conn);
?>

This code uses the mysqli_query() function to execute an insert statement and check whether the data is successfully inserted. If the insertion fails, an error message is output.

Conclusion

PHP and SQL are two indispensable tools in web development. PHP can be integrated with a variety of different types of databases, including MySQL, Oracle, Microsoft SQL Server, and more. By combining PHP and SQL, you can create more powerful and flexible web applications. At the same time, understanding the basics of PHP and SQL can also help you better manage and process data.

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