PHP Database Connection Guide: From Beginner to Expert

PHP Database Connection Guide: From establishing the connection to processing the results. Steps include establishing a connection (mysqli_connect()), executing a query (mysqli_query()), processing the results (mysqli_fetch_array()), and using advanced techniques (prepared statements, transactions, and connection pooling). Practical cases demonstrate connections and queries for user management systems.

PHP Database Connection Guide: From Beginner to Expert

Introduction
A database is anything A key component of modern applications. PHP is a popular programming language that allows you to easily connect and interact with databases. This article will guide you through the various stages of PHP database connection, from basics to advanced techniques.

SQL Introduction
Before connecting to a database, it is important to understand Structured Query Language (SQL). SQL is the standard language for interacting with databases. This article will focus on connection-related SQL statements, such as SELECT, INSERT, and UPDATE.

Phase 1: Establishing a connection
The first step is to use the mysqli_connect() function to establish a connection to the database. This function requires four parameters:

$servername = "localhost";
$username = "user";
$password = "password";
$dbname = "mydb";

$conn = mysqli_connect($servername, $username, $password, $dbname);

Phase 2: Executing the query
Once the connection is established, the SQL query can be executed. Use the mysqli_query() function, which will return a result object.

// SELECT查询
$sql = "SELECT * FROM users";
$result = mysqli_query($conn, $sql);

// INSERT查询
$sql = "INSERT INTO users (name, email) VALUES ('John Doe', 'john@example.com')";
mysqli_query($conn, $sql);

Phase 3: Processing results
The result object contains the query results. The result can be converted to a PHP array using the mysqli_fetch_array() function.

while ($row = mysqli_fetch_array($result)) {
  echo $row['name'] . " " . $row['email'] . "\n";
}

Phase 4: Advanced Tips

• Use prepared statements: Prepared statements can prevent SQL injection attacks and improve query performance performance.
• Transaction: When a series of operations need to be performed, a transaction ensures that either all operations succeed or none succeed.
• Connection pooling: Connection pooling helps reduce the number of connections opened at the same time and improve application performance.

Practical Case: User Management System

Let us create a simple user management system to demonstrate the connection and query concepts.

<?php

// 建立连接
$servername = "localhost";
$username = "user";
$password = "password";
$dbname = "mydb";
$conn = mysqli_connect($servername, $username, $password, $dbname);

// 创建用户
$name = "John Doe";
$email = "john@example.com";
$sql = "INSERT INTO users (name, email) VALUES ('$name', '$email')";
mysqli_query($conn, $sql);

// 获取用户列表
$sql = "SELECT * FROM users";
$result = mysqli_query($conn, $sql);

// 输出列表
echo "<ul>";
while ($row = mysqli_fetch_array($result)) {
  echo "<li>" . $row['name'] . " (" . $row['email'] . ")</li>";
}
echo "</ul>";

?>

Conclusion
PHP database connection is a powerful tool for creating and managing dynamic applications. This article covers the various stages of the connection process, from basic concepts to advanced techniques. Through practical examples, you should already be able to establish connections, execute queries, and process results.

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