你可以给我提供一个php7.0 操作MySQL数据库的类吗？ 必须包含，插入数据，查询数据，删除数据，更新数据。

当然可以，以下是一个简单的 PHP7.0 操作 MySQL 数据库的类，包含插入数据、查询数据、删除数据、更新数据的方法：

class MySQL {
    private $host;
    private $username;
    private $password;
    private $database;
    private $connection;

    public function __construct($host, $username, $password, $database) {
        $this->host = $host;
        $this->username = $username;
        $this->password = $password;
        $this->database = $database;

        $this->connection = mysqli_connect($this->host, $this->username, $this->password, $this->database);
        if (!$this->connection) {
            die("Connection failed: " . mysqli_connect_error());
        }
    }

    public function insert($table, $data) {
        $keys = array_keys($data);
        $values = array_values($data);

        $query = "INSERT INTO $table (" . implode(", ", $keys) . ") VALUES ('" . implode("', '", $values) . "')";
        return mysqli_query($this->connection, $query);
    }

    public function select($table, $conditions = []) {
        $query = "SELECT * FROM $table";
        if (!empty($conditions)) {
            $query .= " WHERE ";
            $i = 0;
            foreach ($conditions as $key => $value) {
                $query .= "$key='$value'";
                if ($i < count($conditions) - 1) {
                    $query .= " AND ";
                }
                $i++;
            }
        }
        $result = mysqli_query($this->connection, $query);
        $rows = mysqli_fetch_all($result, MYSQLI_ASSOC);
        mysqli_free_result($result);
        return $rows;
    }

    public function delete($table, $conditions) {
        $query = "DELETE FROM $table WHERE ";
        $i = 0;
        foreach ($conditions as $key => $value) {
            $query .= "$key='$value'";
            if ($i < count($conditions) - 1) {
                $query .= " AND ";
            }
            $i++;
        }
        return mysqli_query($this->connection, $query);
    }

    public function update($table, $data, $conditions) {
        $query = "UPDATE $table SET ";
        $i = 0;
        foreach ($data as $key => $value) {
            $query .= "$key='$value'";
            if ($i < count($data) - 1) {
                $query .= ", ";
            }
            $i++;
        }
        $query .= " WHERE ";
        $i = 0;
        foreach ($conditions as $key => $value) {
            $query .= "$key='$value'";
            if ($i < count($conditions) - 1) {
                $query .= " AND ";
            }
            $i++;
        }
        return mysqli_query($this->connection, $query);
    }

    public function __destruct() {
        mysqli_close($this->connection);
    }
}

使用方法如下：

$db = new MySQL("localhost", "username", "password", "database");

$data = ["name" => "John", "age" => 30, "email" => "john@example.com"];
$db->insert("users", $data);

$conditions = ["age" => 30, "email" => "john@example.com"];
$users = $db->select("users", $conditions);

$conditions = ["name" => "John"];
$db->delete("users", $conditions);

$data = ["age" => 31];
$conditions = ["name" => "John"];
$db->update("users", $data, $conditions);

以上代码是一个简单的实现，实际使用中需要考虑更多的安全和性能方面的问题。