调用未定义的方法 mysqli::execute_query()

Question

这是我使用的文件：

modeloBd.php

<?php
class modeloBd
{
    private static $server = "127.0.0.1";
    private static $user = "root";
    private static $password = "";
    private static $dbname = "bd";

    protected $conn;

    protected function __construct()
    {
        $conexion = new mysqli(self::$server, self::$user, self::$password, self::$dbname);
        if ($conexion->connect_error) {
            die("Error en la conexión a la base de datos: " . $conexion->connect_error);
        } else {
            $this->conn = $conexion;
        }
    }
}

modeloLogin.php

<?php
require_once "modeloBd.php";

class modeloLogin extends modeloBd
{
    public function __construct()
    {
        parent::__construct();
    }

    public function existe($ci)
    {
        $query = "SELECT * FROM `Usuarios` WHERE ci = ? LIMIT 1";
        $result = $this->conn->execute_query($query, [$ci]);
        $num = mysqli_num_rows($result);
        return $num;
    }

controladorLogin.php

<?php
require '../Modelo/modeloLogin.php';
require '../Modelo/modeloToken.php';

class controladorLogin
{
    public static function chequear($content)
    {
        $ci = $content['post']['ci'];
        $contrasenia = $content['post']['contrasenia'];
        $l = new modeloLogin();
        if ($l->existe($ci)) {
        //code
        }
    }
}

我只需要让我的查询在这里工作：

public function existe($ci)
    {
        $query = "SELECT * FROM `Usuarios` WHERE ci = ? LIMIT 1";
        **$result = $this->conn->execute_query($query, [$ci]);**
        $num = mysqli_num_rows($result);
        return $num;
    }

但是系统却给了我这个错误：

致命错误：未捕获错误：调用 C:\xampp\htdocs\main\Modelo\modeloLogin.php:13 中未定义的方法 mysqli::execute_query() 堆栈跟踪：#0 C:\xampp\htdocs\main\控制