Make connections from one place in PHP

In JSP, if I want to connect to a database, I would create a Java class called DBManager with the following code:

public class DBManager {
    private final static String DB_URL = "jdbc:mysql://localhost:3306/mydb";
    private final static String DB_USERNAME = "root";
    private final static String DB_PASSWORD = "root";
    public static Connection conn = null;
    private static Statement stmt = null;

    /**
     * Tests connection with the database by getting connection using the
     * database url and username and password. And creates a dumb statement and
     * closes it to make sure everything is working fine.
     */
     static {
         try {
            Class.forName("com.mysql.jdbc.Driver");
            conn = DriverManager
                .getConnection(DB_URL, DB_USERNAME, DB_PASSWORD);
            stmt = conn.createStatement();
            stmt.close();
         } catch (Exception e) {
            e.printStackTrace();
         }
     }
}

      

        
        
        
      

    

Now I can easily do something like:

PreparedStatement pstmt = DBManager.conn.prepareStatement("SELECT * FROM USER");

      

        
        
        
      

    

I'm learning PHP on my own, and "most" online tutorials don't really teach you how to do things right.

They all do it the traditional way on every page they need a link to:

$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

// Create connection
$conn = new mysqli($servername, $username, $password, $dbname);

// Check connection
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
}

      

        
        
        
      

    

What's wrong because you want to change your password? Then you have to change it on every page where you used this password.

My question is, how can I do something equivalent / similar to this Java class in PHP?

EDIT:

<?php 
class DBManager {
   public static $conn = null;
   private static $hostname = "localhost";
   private static $username = "root";
   private static $password = "root";
   private static $dbname = "tutorme";

   protected function __construct() {
       try {
           DBManager::$conn = new PDO("mysql:host=localhost;dbname=tutorme", DBManager::$username, DBManager::$password);
           DBManager::$conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
        } catch(PDOException $e) {
            echo "Error: " . $e->getMessage();
        }
    }

    public static function getInstance() {
        if (null === DBManager::$conn) {
            DBManager::$conn = new DBManager();
        }
       return DBManager::$conn;
   }
}
?>

      

        
        
        
      

    

I searched a bit and came up with the above code. However, now when I call

$stmt = DBManager::getInstance()->prepare("INSERT INTO SUBJECT (SubjectTitle, SubjectName) VALUES (:subject,:subj)");

      

        
        
        
      

    

I am getting an error that there is DBManager

no functionprepare()

which means my DBManager::getInstance

returns DBManager object

instead ofPDO conn object