PHP connect class - php

Question

I tried to create a connection class in PHP to connect with the DB data, but one error appears on the lines:
const USER = "{$value['user_DB']}";
const PASS = "{$value['password_DB']}";
Fatal error: Constant expression contains invalid operations in
C:\xampp\htdocs\dev\davinci\classes\Conexao_Teste.class.php on line 21
<?php
require_once"../classes/configDB.class.php";
abstract class conection extends configDB{
private $valor;
private $instanceConfigDB;
public function listDB(){
$valor = $instanceConfigDB->listconfigDB();
foreach($valor as $value){
echo "Banco: ID:{$value['id_db']} - Hostname:{$value['hostname']} - DBNAME:{$value['dbname']} - User:{$value['user_DB']} - PASS:{$value['password_DB']}<br>";
}
}
const USER = "{$value['user_DB']}";
const PASS = "{$value['password_DB']}";
private static $instance = null;
private static function conect(){
try {
if(self:: $instance==null):
$dsn = "mysql:host={$value['hostname']};dbname={$value['dbname']};charset=utf8";
self::$instance = new PDO($dsn, self::USER, self::PASS);
self::$instance->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
endif;
} catch (PDOException $e) {
echo "Erro: " . $e->getMessage();
}
return self::$instance;
}
protected static function getDB() {
return self::conect();
}
}
?>

Answer 1

You should use
define('USER', "{$value['user_DB']}");
As const would be evaluated at compile time where as define would be evaluated at run time.

Answer 2

You are trying to use $value[] outside it's defined scope, and that is why you are getting those errors.
$value[] is declared in method listDB(). If you want to use that value outside of the method you'd have to declare variables outside the method.
//Declaring variables and constants
private $valor;
private $instanceConfigDB;
private $username;
private $pass;
private $hostname;
private $dbname;
public function listDB(){
$valor = $instanceConfigDB->listconfigDB();
foreach($valor as $value){
echo "Banco: ID:{$value['id_db']} - Hostname:{$value['hostname']} - DBNAME: {$value['dbname']} - User:{$value['user_DB']} - PASS:{$value['password_DB']}<br>";
//Initialize your data
$username = $value[user_DB];
$pass = $value[password_DB];
....
}
}
At least this way, your data is then accessible outside your method
Your connect method would then look like this:
private static function conect(){
try {
if(self:: $instance==null):
$dsn = "mysql:host={$hostname};dbname={$dbname};charset=utf8";
self::$instance = new PDO($dsn, self::$username, self::$pass);
self::$instance->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
endif;
} catch (PDOException $e) {
echo "Erro: " . $e->getMessage();
}