php mysqli oops 概念连接

Question

这个问题在这里已经有了答案:





mysql_fetch_array()/mysql_fetch_assoc()/mysql_fetch_row()/mysql_num_rows etc... expects parameter 1 to be resource

(31 个回答)


6年前关闭。




config.php 文件

<?php
Class Config
{
    private $_host;
    private $_user;
    private $_password;
    private $_db;

    public function __constructor()
    {
        $this->_host = 'localhost';
        $this->_user = 'root';
        $this->_password = '';
        $this->_db = 'test';
    }

    public function connectDB()
    {
        $connect = new mysqli($this->_host, $this->_user, $this->_password, $this->_db);
        if (!$connect) {
            die('Connection Error : ' . $connect->mysql_error());
        } else {
            echo 'Connection Success';
        }
        return $connect;
    }
}
?>

index.php 文件

<?php
include 'config.php';
$conn = new Config();
$conn = $conn->connectDB();
$sql = "SELECT name, matric_no FROM users";
$result = mysqli_query($conn, $sql);
if (mysqli_num_rows($result) > 0) {
    while ($row = mysqli_fetch_assoc($result)) {
        echo 'Name : ' . $row['name'] . ' - Matric No : ' . $row['matric_no'] . '<br>';
    }
} ?>

显示错误:

Connection Success
Warning: mysqli_num_rows() expects parameter 1 to be mysqli_result, boolean given in D:\xampp\htdocs\test\index.php on line 10

有什么解决办法吗？

Answer 1

构造函数应为:

public function __construct()

而不是 public function __constructor()

根据手册: http://php.net/manual/en/language.oop5.decon.php关于构造函数和析构函数

<?php
Class Config
{
    private $_host;
    private $_user;
    private $_password;
    private $_db;

    public function __construct()
    {
        $this->_host = 'localhost';
        $this->_user = 'root';
        $this->_password = '';
        $this->_db = 'test';
    }

    public function connectDB()
    {
        $connect = new mysqli($this->_host, $this->_user, $this->_password, $this->_db);
        if (!$connect) {
           return 'Connection Error : ' . $connect->mysql_error();
        } else {
           return $connect;
        }

    }
}
?>

并在 Index.php 文件中通过 var_dump/print_r 检查连接是否成功

<?php
include 'config.php';
$conn = new Config();
$conn = $conn->connectDB();
print_r($conn); break; //Remove this line if db connxn is succesfull

$sql = "SELECT name, matric_no FROM users";
$result = mysqli_query($conn, $sql);
if (mysqli_num_rows($result) > 0) {
    while ($row = mysqli_fetch_assoc($result)) {
        echo 'Name : ' . $row['name'] . ' - Matric No : ' . $row['matric_no'] . '<br>';
    }
} ?>

将执行流程牢记在心，逐点调试以找出问题所在。