php 链式方法

class DB {
    private $query;

    public function select($table) {
        $this->query = "SELECT * FROM $table";
        return $this;
    }

    public function where($condition) {
        $this->query .= " WHERE $condition";
        return $this;
    }

    public function execute() {
        // 执行查询并返回结果
        echo $this->query; // 实际应用中应执行数据库查询
        return $this;
    }
}

$db = new DB();
$db->select('users')->where('id = 1')->execute();

public function select($table) {
    $this->query = "SELECT * FROM $table";
    echo "SELECT called with table: $table\n"; // 日志记录
    return $this;
}

public function where($condition) {
    if (empty($this->query)) {
        throw new Exception("Query not initialized");
    }
    $this->query .= " WHERE $condition";
    return $this;
}