在mySQLI中的null上调用成员函数准备()

Question

我想使用mysqli从数据库中获取数据。

class.php

的代码

class main{
    public $host="localhost";
    public $username="root";
    public $password="";
    public $db_name= "db_tvw";
    private $img_path    = 'slider_img_upload/';
    public function __construct(){
        $this->run= new mysqli($this->host, $this->username, $this->password, $this->db_name);
        if (mysqli_connect_errno()){
            echo "database connection is fail";
            exit;
        }
    }
    public function select_data_from_db($table_name ,$run){
        $stmt=$run->prepare("SELECT * FROM ".$table_name); 
        $stmt->execute();
        $result = $stmt->get_result();
        $total_count=$result->num_rows;
        $result= array();
        if($total_count>0){
            while ($row = mysqli_fetch_array($query)) {
                $result[] = $row;
            }
        }
        return $result;
    }

---

index.php

的代码

<?php $myrow=$obj->select_data_from_db("home_slider",$run); ?>
<tr>
    <td><?php echo  $myrow['id']; ?> </td>
    <td><?php echo  $myrow['title']; ?> </td>
    <td><?php echo  $myrow['description']; ?> </td>
</tr>

---

我遇到的错误：

Notice: Undefined variable: run in 
D:Xampphtdocsadminslider_fetch_data.php on line 24.
Fatal error: Call to a member function prepare() on null in 
D:Xampphtdocsadminconfig.php on line 116.

Answer 1

因为在您的class.php上，您使用此代码初始化运行

$this->run= new mysqli($this->host, $this->username, $this->password, $this->db_name);

我认为您不需要

public function select_data_from_db($table_name ,$run){}

删除第二个参数

---

应该是这个

public function select_data_from_db($table_name){}

---

这是正确的代码(如果我没有错，而mysqli工作(

class.php

class main{
    public $host="localhost";
    public $username="root";
    public $password="";
    public $db_name= "db_tvw";
    private $img_path    = 'slider_img_upload/';
    public function __construct(){
        $this->run= new mysqli($this->host, $this->username, $this->password, $this->db_name);
        if (mysqli_connect_errno()){
            echo "database connection is fail";
            exit;
        }
    }
    public function select_data_from_db($table_name){
        $stmt=$this->run->prepare("SELECT * FROM ".$table_name); 
        $stmt->execute();
        $result = $stmt->get_result();
        $total_count=$result->num_rows;
        $result= array();
        if($total_count>0){
            while ($row = mysqli_fetch_array($query)) {
                $result[] = $row;
            }
        }
        return $result;
    }
...

---

在index.php上

<?php $myrow=$obj->select_data_from_db("home_slider"); ?>
<tr>
    <td><?php echo  $myrow['id']; ?> </td>
    <td><?php echo  $myrow['title']; ?> </td>
    <td><?php echo  $myrow['description']; ?> </td>
</tr>

Answer 2

<?php
    $myrow = new main();
    $myrow=$obj->select_data_from_db("home_slider",$myrow->run);
?>
<tr>
    <td><?php echo  $myrow['id']; ?> </td>
    <td><?php echo  $myrow['title']; ?> </td>
    <td><?php echo  $myrow['description']; ?> </td>
</tr>

您可以尝试