Discussion on the underlying development principles of PHP: database connection and query optimization technology

Discussion on the underlying development principles of PHP: database connection and query optimization technology

Introduction:
PHP is an advanced scripting language that is widely used in the field of Web development . In the underlying development of PHP, database connection and query optimization are important and common tasks. This article will discuss two aspects: database connection and query optimization, and provide code examples with examples to help readers better understand and apply these technologies.

1. Database connection technology

1. PDO (PHP Data Objects) connection method
   PDO is PHP’s own database extension, supporting a variety of databases, such as MySQL, SQLite, etc. . It provides a unified interface to connect and operate different types of databases, and is flexible and secure.

The following is a simple sample code showing how to use PDO for database connection:

$dsn = 'mysql:host=localhost;dbname=test';
$user = 'root';
$pass = 'password';

try {
    $pdo = new PDO($dsn, $user, $pass);
    echo '数据库连接成功！';
} catch(PDOException $e) {
    echo '数据库连接失败：' . $e->getMessage();
}

2. MySQLi (MySQL Improved) connection method
   MySQLi is a modification of the original An improved and enhanced version of the MySQL extension, providing more features and performance optimizations, supporting object-oriented and procedural programming styles.

The following is a simple sample code showing how to use MySQLi for database connection:

$mysqli = new mysqli("localhost", "root", "password", "test");

if ($mysqli->connect_errno) {
    echo '数据库连接失败：' . $mysqli->connect_error;
} else {
    echo '数据库连接成功！';
}

2. Query optimization technology

1. Use of index
   Database index is the key to improving query efficiency. When designing a database, appropriate indexes can effectively narrow the query scope and improve query speed. For frequently queried fields, such as IDs, keywords, etc., it is recommended to create indexes.

The following is a sample code that demonstrates how to create an index in MySQL:

CREATE INDEX idx_name ON users (name);

2. Prepared Statement
   A prepared statement is a tool used to optimize database queries. important technology. It can reduce repeated parsing and compilation processes, improve the efficiency of database queries, and avoid SQL injection attacks.

The following is a simple sample code showing how to use prepared statements to perform database queries:

$stmt = $pdo->prepare('SELECT * FROM users WHERE id = :id');
$stmt->bindParam(':id', $id, PDO::PARAM_INT);
$stmt->execute();
$result = $stmt->fetchAll(PDO::FETCH_ASSOC);

3. Avoid unnecessary queries
   When performing database queries , try to avoid unnecessary queries and only query the required fields and data. For example, don't use SELECT *, but explicitly specify the fields you want to query.

The following is a sample code that demonstrates how to query only the required fields:

$stmt = $pdo->prepare('SELECT name, email FROM users');
$stmt->execute();
$result = $stmt->fetchAll(PDO::FETCH_ASSOC);

Conclusion:
This article mainly introduces the technology of database connection and query optimization in the underlying development of PHP . By rationally selecting and using database connection methods, using indexes, preprocessing statements, and avoiding unnecessary queries, database performance and query efficiency can be effectively improved. Developers can flexibly apply these technologies according to actual project needs, thereby improving the overall performance of the application.

References:

• PHP official documentation: https://www.php.net/
• PDO official documentation: https://www.php. net/manual/zh/book.pdo.php
• MySQLi official documentation: https://www.php.net/manual/zh/book.mysqli.php

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