PHP trait DTO：提升数据传输层的可靠性与可扩展性

<?php
trait ValidationTrait {
    // 验证字段是否为空
    public function validateRequired($field, $value) {
        if (empty($value)) {
            throw new Exception("$field不能为空");
        }
    }
    
    // 验证字段的长度是否符合要求
    public function validateLength($field, $value, $minLength, $maxLength) {
        $length = strlen($value);
        if ($length < $minLength || $length > $maxLength) {
            throw new Exception("$field的长度必须在$minLength到$maxLength之间");
        }
    }
}

class UserDTO {
    use ValidationTrait;
    
    private $username;
    private $email;
    
    public function __construct($username, $email) {
        $this->validateRequired('用户名', $username);
        $this->validateLength('用户名', $username, 6, 20);
        
        $this->validateRequired('邮箱', $email);
        $this->validateLength('邮箱', $email, 6, 50);
        
        $this->username = $username;
        $this->email = $email;
    }
    
    public function getUsername() {
        return $this->username;
    }
    
    public function getEmail() {
        return $this->email;
    }
}

// 使用UserDTO类来创建用户对象
$user = new UserDTO('john123', 'john@example.com');

// 获取用户对象的属性值
$username = $user->getUsername();
$email = $user->getEmail();

// 输出用户对象的属性值
echo "用户名: $username" . PHP_EOL;
echo "邮箱: $email" . PHP_EOL;

?>