php类中访问自己类内的属性或者方法都需要加 $this->
class UserImpl{ private $conn; private $sql; private $result; function connect(){ $servername = "localhost"; $username = "root"; $password = "12345"; $dbname = "db"; // 创建连接 $con = new mysqli($servername, $username, $password, $dbname); // 检测连接 if ($con->connect_error) { die("连接失败: " . $con->connect_error); } $this->$conn = $con; } function insert($name, $password){ $sql = "INSERT INTO user (name, password) VALUES ('$name', '$password')"; if ($this->$conn->query($sql) === TRUE) { echo "新记录插入成功"; } else { echo "Error: " . $sql . "<br>" . $this->$conn->error; } $this->$conn->close(); } function select($str){ $sql = "select * from user where".$str; $result = $conn->query($sql); if($result->num_rows > 0){ return $result; }else{ return 0; } } function delete($str){ $sql = "delete from user where".$str; if($conn->query($sql) == TRUE){ echo "SUCCESS"; }else{ echo "delete".$conn->error; } } }