PHP learning experience: how to write a good function library

PHP Learning Experience: How to Write a Good Function Library

When writing PHP code, you often encounter some repetitive work, such as databases from different pages Connection, data filtering, file reading and writing, etc. In order to improve the reusability and maintainability of the code, we can encapsulate these functions in function libraries to facilitate reuse in different projects.

This article will introduce some tips and precautions for writing good function libraries, and provide some code examples to help understanding.

1. Naming and function definition of functions
   Naming is a very important link when writing a function library. The function name should describe the function of the function concisely and concisely, making it easier for other developers to use and understand it. Try to avoid names that are too obscure or too simple.

The function definition of a function should be clear and concise, and try to follow the single responsibility principle, that is, a function only does one thing. This improves code readability and maintainability.

The following is the naming and function definition of a sample function library:

// 连接数据库
function connectDatabase($host, $username, $password, $dbname) {
    // ...
}

// 过滤HTML标签
function filterHTMLTags($input) {
    // ...
}

// 读取文件内容
function readFileContent($filename) {
    // ...
}

2. Parameter verification and default value setting
   When writing a function library, you need to verify the incoming parameters Perform validation and default settings. This can increase the robustness and fault tolerance of the code.

The following is the code for parameter verification and default value setting of a sample function library:

// 连接数据库
function connectDatabase($host = 'localhost', $username = 'root', $password = '', $dbname = '') {
    // 参数验证
    if (empty($host) || empty($username)) {
        throw new Exception('Invalid parameters');
    }

    // ...
}

// 过滤HTML标签
function filterHTMLTags($input) {
    // 参数验证
    if (empty($input)) {
        return '';
    }

    // ...
}

// 读取文件内容
function readFileContent($filename, $defaultValue = '') {
    // 参数验证
    if (!file_exists($filename)) {
        return $defaultValue;
    }

    // ...
}

3. Error handling and exception throwing
   When writing a function library, you need Consider various possible error conditions and perform appropriate error handling or exception throwing. This improves the robustness and fault tolerance of your code.

The following is the error handling and exception throwing code of a sample function library:

// 连接数据库
function connectDatabase($host, $username, $password, $dbname) {
    // 错误处理
    $link = mysqli_connect($host, $username, $password, $dbname);
    if (!$link) {
        throw new Exception('Failed to connect to database');
    }

    // ...
}

// 过滤HTML标签
function filterHTMLTags($input) {
    // 错误处理
    if (empty($input)) {
        throw new InvalidArgumentException('Invalid input');
    }

    // ...
}

// 读取文件内容
function readFileContent($filename) {
    // 错误处理
    if (!file_exists($filename)) {
        throw new Exception('File not found');
    }

    // ...
}

4. Documentation comments and code comments
   In order to facilitate other developers to use and To understand the function library, you need to add appropriate documentation comments and code comments to each function. Documentation comments should include function description, parameter description, return value description, etc. of the function. Code comments should explain the logic and intent of the code.

The following is the code of the documentation comments and code comments of a sample function library:

/**
 * 连接数据库
 *
 * @param string $host     主机名
 * @param string $username 用户名
 * @param string $password 密码
 * @param string $dbname   数据库名称
 * @return resource 数据库连接资源
 * @throws Exception 连接失败时抛出异常
 */
function connectDatabase($host, $username, $password, $dbname) {
    // ...
}

/**
 * 过滤HTML标签
 *
 * @param string $input 输入字符串
 * @return string 过滤后的字符串
 * @throws InvalidArgumentException 输入为空时抛出异常
 */
function filterHTMLTags($input) {
    // ...
}

/**
 * 读取文件内容
 *
 * @param string $filename 文件名
 * @return string 文件内容
 * @throws Exception 文件不存在时抛出异常
 */
function readFileContent($filename) {
    // ...
}

Through the above techniques and examples, you can write a concise, robust and easy-to-use function libraries to improve code reusability and maintainability. I hope this article will be helpful to everyone in writing good function libraries!

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