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PHP 学习笔记 - 专业版
2025-10-19
2025-10-19

PHP 学习笔记 - 专业版

1. PHP 基础语法与特性

1.1 PHP 标记与输出

<?php
// 标准PHP标记
echo "Hello, World!"; // 输出字符串
print_r($array); // 打印变量信息
var_dump($variable); // 详细变量信息
?>

1.2 变量与数据类型

<?php
// 变量声明（弱类型）
$string = "字符串";
$integer = 42;
$float = 3.14;
$boolean = true;
$array = [1, 2, 3];
$assocArray = ['name' => 'John', 'age' => 25];
$null = null;

// 类型检测
is_string($string); // true
is_int($integer); // true
is_array($array); // true

// 类型转换
$number = (int) "123";
$text = (string) 456;
?>

1.3 运算符

<?php
// 比较运算符
$a == $b;   // 值相等
$a === $b;  // 值和类型都相等
$a != $b;   // 值不相等
$a !== $b;  // 值或类型不相等

// 太空船运算符 (PHP 7+)
$result = $a <=> $b;
// $a < $b: -1, $a == $b: 0, $a > $b: 1

// 空合并运算符 (PHP 7+)
$username = $_GET['user'] ?? 'anonymous';

// 空合并赋值运算符 (PHP 7.4+)
$array['key'] ??= 'default';
?>

2. 函数编程

2.1 函数定义与使用

<?php
// 基本函数
function calculateSum(int $a, int $b): int {
    return $a + $b;
}

// 默认参数
function greet(string $name, string $greeting = "Hello"): string {
    return "$greeting, $name!";
}

// 可变长度参数 (PHP 5.6+)
function sum(...$numbers): float {
    return array_sum($numbers);
}

// 严格类型声明
declare(strict_types=1);
function strictAdd(int $a, int $b): int {
    return $a + $b;
}
?>

2.2 匿名函数与闭包

<?php
// 匿名函数
$square = function($n) {
    return $n * $n;
};

// 箭头函数 (PHP 7.4+)
$cube = fn($n) => $n ** 3;

// 闭包使用use传递变量
$multiplier = 2;
$double = function($n) use ($multiplier) {
    return $n * $multiplier;
};
?>

3. 面向对象编程

3.1 类与对象

<?php
class User {
    // 属性声明
    private string $name;
    protected string $email;
    public int $age;
    
    // 构造函数 (PHP 8 构造函数属性提升)
    public function __construct(
        string $name,
        string $email,
        int $age = 0
    ) {
        $this->name = $name;
        $this->email = $email;
        $this->age = $age;
    }
    
    // 方法
    public function getName(): string {
        return $this->name;
    }
    
    public function setEmail(string $email): void {
        if (filter_var($email, FILTER_VALIDATE_EMAIL)) {
            $this->email = $email;
        }
    }
    
    // 静态方法
    public static function createAnonymous(): self {
        return new self('Anonymous', 'anon@example.com');
    }
    
    // 魔术方法
    public function __toString(): string {
        return "User: {$this->name} ({$this->email})";
    }
}

// 使用
$user = new User("John", "john@example.com", 25);
echo $user->getName();
?>

3.2 继承与多态

<?php
abstract class Person {
    protected string $name;
    
    public function __construct(string $name) {
        $this->name = $name;
    }
    
    abstract public function getRole(): string;
}

class Student extends Person {
    private string $studentId;
    
    public function __construct(string $name, string $studentId) {
        parent::__construct($name);
        $this->studentId = $studentId;
    }
    
    public function getRole(): string {
        return "Student";
    }
    
    // final 方法，禁止子类重写
    final public function getStudentId(): string {
        return $this->studentId;
    }
}

// 接口
interface Loggable {
    public function log(string $message): void;
}

class Teacher extends Person implements Loggable {
    public function getRole(): string {
        return "Teacher";
    }
    
    public function log(string $message): void {
        echo "[LOG] $message\n";
    }
}
?>

3.3 特性 (Traits)

<?php
trait Logger {
    public function log(string $message): void {
        echo "[".date('Y-m-d H:i:s')."] $message\n";
    }
}

trait Timestamp {
    public function getTimestamp(): string {
        return date('Y-m-d H:i:s');
    }
}

class Application {
    use Logger, Timestamp;
    
    public function run(): void {
        $this->log("Application started");
        echo "Current time: " . $this->getTimestamp();
    }
}
?>

4. 错误与异常处理

4.1 异常处理

<?php
class CustomException extends Exception {
    public function __construct($message, $code = 0, Exception $previous = null) {
        parent::__construct($message, $code, $previous);
    }
    
    public function __toString(): string {
        return __CLASS__ . ": [{$this->code}]: {$this->message}\n";
    }
}

class DataProcessor {
    /**
     * @throws CustomException
     */
    public function process(array $data): bool {
        if (empty($data)) {
            throw new CustomException("Data cannot be empty");
        }
        
        try {
            // 处理逻辑
            return true;
        } catch (InvalidArgumentException $e) {
            throw new CustomException("Processing failed", 0, $e);
        }
    }
}

// 使用异常处理
try {
    $processor = new DataProcessor();
    $processor->process([]);
} catch (CustomException $e) {
    error_log($e->getMessage());
    echo "Error: " . $e->getMessage();
} finally {
    echo "Processing completed\n";
}
?>

4.2 错误处理

<?php
// 自定义错误处理函数
set_error_handler(function($errno, $errstr, $errfile, $errline) {
    throw new ErrorException($errstr, 0, $errno, $errfile, $errline);
});

// 自定义异常处理函数
set_exception_handler(function($exception) {
    error_log("Uncaught exception: " . $exception->getMessage());
    http_response_code(500);
    echo "An error occurred. Please try again later.";
});

// 关闭错误处理
restore_error_handler();
restore_exception_handler();
?>

5. 安全编程实践

5.1 输入验证与过滤

<?php
class InputValidator {
    public static function validateEmail(string $email): bool {
        return filter_var($email, FILTER_VALIDATE_EMAIL) !== false;
    }
    
    public static function sanitizeString(string $input): string {
        return htmlspecialchars(strip_tags(trim($input)), ENT_QUOTES, 'UTF-8');
    }
    
    public static function validateInteger($value, int $min = null, int $max = null): ?int {
        $options = [];
        if ($min !== null) $options['min_range'] = $min;
        if ($max !== null) $options['max_range'] = $max;
        
        return filter_var($value, FILTER_VALIDATE_INT, ['options' => $options]);
    }
}

// 使用
$email = InputValidator::validateEmail($_POST['email']);
$name = InputValidator::sanitizeString($_POST['name']);
?>

5.2 密码安全

<?php
class PasswordManager {
    private const COST = 12;
    
    public static function hash(string $password): string {
        return password_hash($password, PASSWORD_BCRYPT, ['cost' => self::COST]);
    }
    
    public static function verify(string $password, string $hash): bool {
        return password_verify($password, $hash);
    }
    
    public static function needsRehash(string $hash): bool {
        return password_needs_rehash($hash, PASSWORD_BCRYPT, ['cost' => self::COST]);
    }
}
?>

6. 数据库操作 (PDO)

6.1 数据库连接与查询

<?php
class Database {
    private PDO $pdo;
    
    public function __construct(
        string $host,
        string $dbname,
        string $username,
        string $password
    ) {
        $dsn = "mysql:host=$host;dbname=$dbname;charset=utf8mb4";
        
        $options = [
            PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
            PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
            PDO::ATTR_EMULATE_PREPARES => false,
        ];
        
        try {
            $this->pdo = new PDO($dsn, $username, $password, $options);
        } catch (PDOException $e) {
            throw new PDOException($e->getMessage(), (int)$e->getCode());
        }
    }
    
    public function getUsers(): array {
        $stmt = $this->pdo->prepare("SELECT id, name, email FROM users WHERE active = :active");
        $stmt->execute(['active' => 1]);
        return $stmt->fetchAll();
    }
    
    public function createUser(array $userData): bool {
        $sql = "INSERT INTO users (name, email, password) VALUES (:name, :email, :password)";
        $stmt = $this->pdo->prepare($sql);
        
        return $stmt->execute([
            'name' => $userData['name'],
            'email' => $userData['email'],
            'password' => PasswordManager::hash($userData['password'])
        ]);
    }
}
?>

7. 现代 PHP 特性

7.1 PHP 8+ 新特性

<?php
// 命名参数 (PHP 8.0)
function createUser(string $name, string $email, int $age = 0) {
    // ...
}

createUser(name: "John", email: "john@example.com");

// 属性 (PHP 8.0)
class UserDTO {
    public function __construct(
        public string $name,
        public string $email,
        public int $age = 0
    ) {}
}

// 匹配表达式 (PHP 8.0)
$status = match($httpCode) {
    200, 201 => 'success',
    400, 401, 403 => 'client_error',
    500, 502 => 'server_error',
    default => 'unknown'
};

// 构造器属性提升 (PHP 8.0)
class Order {
    public function __construct(
        private int $id,
        private DateTime $createdAt = new DateTime()
    ) {}
}

// 只读属性 (PHP 8.1)
readonly class UserProfile {
    public function __construct(
        public string $username,
        public DateTime $createdAt
    ) {}
}
?>

8. 性能优化与最佳实践

8.1 代码优化

<?php
// 使用预编译语句
$stmt = $pdo->prepare("SELECT * FROM users WHERE id = ?");
$stmt->execute([$userId]);

// 批量插入
$values = [];
$placeholders = [];
$data = [];

foreach ($users as $index => $user) {
    $placeholders[] = "(?, ?, ?)";
    array_push($data, $user['name'], $user['email'], $user['age']);
}

$sql = "INSERT INTO users (name, email, age) VALUES " . implode(',', $placeholders);
$stmt = $pdo->prepare($sql);
$stmt->execute($data);
?>

8.2 缓存策略

<?php
class CacheManager {
    private Redis $redis;
    
    public function __construct() {
        $this->redis = new Redis();
        $this->redis->connect('127.0.0.1', 6379);
    }
    
    public function remember(string $key, int $ttl, callable $callback) {
        $cached = $this->redis->get($key);
        
        if ($cached !== false) {
            return unserialize($cached);
        }
        
        $result = $callback();
        $this->redis->setex($key, $ttl, serialize($result));
        
        return $result;
    }
}
?>

9. 测试与调试

9.1 单元测试示例 (PHPUnit)

<?php
use PHPUnit\Framework\TestCase;

class UserTest extends TestCase {
    public function testUserCreation(): void {
        $user = new User("John", "john@example.com");
        
        $this->assertEquals("John", $user->getName());
        $this->assertEquals("john@example.com", $user->getEmail());
    }
    
    public function testInvalidEmail(): void {
        $this->expectException(InvalidArgumentException::class);
        new User("John", "invalid-email");
    }
}
?>

总结

这份学习笔记涵盖了 PHP 开发的核心概念，从基础语法到高级特性，包括：

  • 现代 PHP 语法和类型系统

  • 面向对象编程原则

  • 安全编程实践

  • 数据库交互

  • 错误和异常处理

  • 性能优化技巧

  • 测试方法

持续学习和实践这些概念将帮助您成为专业的 PHP 开发者。建议结合实际项目应用这些知识，并关注 PHP 官方文档以了解最新特性更新。

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