PHP 无法使用 mysqli_connect 连接到数据库

Question

i'm facing with this problem that when i'm trying connect to database with constants, then it's showing this in my VS editor: Undefined constant 'DB_HOST', 'DB_USER', 'DB_PASS', 'DB_NAME'.

Here my code:

<?php

$db['db_host'] = "localhost";
$db['db_user'] = "root";
$db['db_pass'] = "";
$db['db_name'] = "cms";

foreach($db as $key => $value){
     define(strtoupper($key), $value);
}

$connection = mysqli_connect(DB_HOST, DB_USER, DB_PASS, DB_NAME);

?>

I tried change

$connection = mysqli_connect(DB_HOST, DB_USER, DB_PASS, DB_NAME);

to

$connection = mysqli_connect('DB_HOST', 'DB_USER', 'DB_PASS', 'DB_NAME');

After this step, my localhost was showing this error below:

Warning: mysqli_connect(): php_network_getaddresses: getaddrinfo failed: No such host is known. in C:\xampp\htdocs\cms\includes\db.php on line 12

Warning: mysqli_connect(): (HY000/2002): php_network_getaddresses: getaddrinfo failed: No such host is known. in C:\xampp\htdocs\cms\includes\db.php on line 12

Could you please help me solve this error, or tell me what i'm doing wrong

Answer 1

it seems to be an issue with the Visual Studio Code. The code works and connects to the db OK but shows DB_HOST etc as undefined with a wiggly red 'naughty' line. So I got rid of the warning by defining the constants without a loop or associative array.

define("DB_HOST", 'localhost');
define("DB_USER", 'root');
define("DB_PASS", '');
define("DB_NAME", 'cms');

Answer 2

Assuming you're developing locally (or MySQL/MariaDB is available on localhost port 3306), it looks like you need to determine which IP address you're using. In command line, try:

c:\>ping localhost

You should see a response like:

Pinging localhost with 32 bytes of data:
Reply from 127.0.0.1: bytes=32 time<1ms TTL=128

Use the address stated in the reply (ie, 127.0.0.1 ). Note that your localhost might not be set up right. If you're using XAMPP, ensure that the MySQL service is running first. Check the mysql_error.log file and see what that tells you.

<?php
    $db = [
        'db_host' => '127.0.0.1', /* or the ip address to the MySQL service */
        'db_port' => '3306',
        'db_user' => 'root',
        'db_pass' => '',
        'db_name' => 'cms'
    ];

    $con = new mysqli($db['db_host'], $db['db_user'], $db['db_pass'], $db['db_name'], $db['db_port']);

    if ($error = mysqli_connect_error()) {
        echo '<pre>' . print_r($error, TRUE) . '</pre>';
    }