警告:mysqli_query() 期望参数 1 为 mysqli，第 14 行 C:xampphtdocsFinaldata.php 中给出的 null

I need help to figure out why this is error

<?php
    class data
    {
        private $db;
        public $nama, $password, $alamat, $jk, $kodepos, $alasan, $email;
        function _construct($db)
        {
            $this->db = $db;
        }
        public function input_data()
        {
            $query = "INSERT INTO data (nama, password, alamat, jeniskelamin, kodepos, alasan, email)VALUES('$this->nama', '$this->password',
            '$this->alamat', '$this->jk', '$this->kodepos', '$this->alasan', '$this->email')";
            $insert = mysqli_query($this->db, $query);
            return $insert;
        }
        public function lihat_data()
        {
            $query = "SELECT * FROM data ORDER BY id";
            $view = mysqli_query($this->db, $query);
            return $view;
        }
    }
?>

推荐答案

您的警告表示您的连接失败！那是因为它从未被制作过！

function __construct($db) {
       //^^You need 2 underscores
    $this->db = $db;
}