Does the PHP's define() not work with PDO connection string? - php

Question

I was using the PHP's define() to define constants for my PDO connection string, ie. in mysqli. However, it just didn't seem to work. I kept getting the error: Connection failed: SQLSTATE[HY000] [1045] Access denied for user 'root'#'localhost' (using password: NO) when I used the code below:
The PDO connection string would work when I didn't use PHP's define() function to pass in my connection variables. I'm using PHP 7, MySQL 8, and Apache 2.4.
Problem code below:
error_reporting(E_ALL); //check all type of errors
ini_set('display_errors', 1); // display those if any happen
//Database Connection Constant
define('DB_HOST', 'localhost');
define('DB_USER', 'root');
define('DB_PASS', 'root');
define('DB_NAME', 'gallery_db');
echo DB_PASS;
//phpinfo();
//$conn = mysqli_connect(DB_HOST,DB_USER,DB_PASS,DB_NAME);
try {
$dbc = new PDO("mysql:host=" . DB_HOST . ";dbname=" . DB_NAME . "," . DB_USER, DB_PASS);
// set the PDO error mode to exception
$dbc->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
if ($dbc) {
echo "connected";
}
} catch (PDOException $e) {
echo "Connection failed: " . $e->getMessage();
}
Working Connection Code:
$servername = 'localhost';
$username = 'root';
$password = 'root';
$dbn = 'gallery_db';
//phpinfo();
try {
$dbc = new PDO("mysql:host=$servername;dbname=$dbn", $username, $password,
array(
PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
PDO::ATTR_PERSISTENT => false
));
// set the PDO error mode to exception
$dbc->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
if ($dbc) {
echo "connected";
}
} catch (PDOException $e) {
echo "Connection failed: " . $e->getMessage();
}
Why does PHP define() not work in PDO's connection string?

Answer 1

In the first instance you try this:
$dbc = new PDO("mysql:host=".DB_HOST.";dbname=".DB_NAME.",". DB_USER, DB_PASS);
This only has two arguments, but PDO needs 3:
<?php
$dbh = new PDO('mysql:host=localhost;dbname=test', $user, $pass);
?>
https://php.net/manual/en/pdo.connections.php
What happens is that your password constant works but went into the username part of the connection.
Fix:
$dbc = new PDO("mysql:host=".DB_HOST.";dbname=".DB_NAME, DB_USER, DB_PASS);

Answer 2

Change
$dbc = new PDO("mysql:host=".DB_HOST.";dbname=".DB_NAME.",". DB_USER, DB_PASS);
to
$dbc = new PDO("mysql:host=".DB_HOST.";dbname=".DB_NAME, DB_USER, DB_PASS);