[php] connecting to phpMyAdmin database with PHP/MySQL

I've made a database using phpMyAdmin , now I want to make a register form for my site where peaple can register .I know how to work with input tags in HTML and I know how to insert data into a database but my problem is that I don't know how I can connect to the database that is already made in phpMyAdmin.

Set up a user, a host the user is allowed to talk to MySQL by using (e.g. localhost), grant that user adequate permissions to do what they need with the database .. and presto.

The user will need basic CRUD privileges to start, that's sufficient to store data received from a form. The rest of the permissions are self explanatory, i.e. permission to alter tables, etc. Give the user no more, no less power than it needs to do its work.

Connect to MySQL

<?php

/*** mysql hostname ***/
$hostname = 'localhost';

/*** mysql username ***/
$username = 'username';

/*** mysql password ***/
$password = 'password';

try {
    $dbh = new PDO("mysql:host=$hostname;dbname=mysql", $username, $password);
    /*** echo a message saying we have connected ***/
    echo 'Connected to database';
    }
catch(PDOException $e)
    {
    echo $e->getMessage();
    }
?>

Also mysqli_connect() function to open a new connection to the MySQL server.

<?php
// Create connection
$con=mysqli_connect(host,username,password,dbname); 

// Check connection
if (mysqli_connect_errno())
  {
  echo "Failed to connect to MySQL: " . mysqli_connect_error();
  }
?> 

This (mysql_connect, mysql_...) extension is deprecated as of PHP 5.5.0, and will be removed in the future. Instead, the MySQLi or PDO_MySQL extension should be used.
(ref: http://php.net/manual/en/function.mysql-connect.php)

• Object Oriented:

  $mysqli = new mysqli("host", "user", "password");
  $mysqli->select_db("db");
  

• Procedural:

  $link = mysqli_connect("host","user","password") or die(mysqli_error($link)); 
  mysqli_select_db($link, "db");
  

$db = new mysqli('Server_Name', 'Name', 'password', 'database_name');