how to connect pdo php database

1<?php
2$servername = "localhost";
3$username = "username";
4$password = "password";
5
6try {
7    $conn = new PDO("mysql:host=$servername;dbname=myDB", $username, $password);
8    // set the PDO error mode to exception
9    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
10    echo "Connected successfully";
11    }
12catch(PDOException $e)
13    {
14    echo "Connection failed: " . $e->getMessage();
15    }
16?>

1$host     = "localhost";//Ip of database, in this case my host machine    
2$user     = "root";	//Username to use
3$pass     = "qwerty";//Password for that user
4$dbname   = "DB";//Name of the database
5
6try {
7    $connection = new PDO("mysql:host=$host;dbname=$dbname", $user, $pass);
8    $connection->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
9
10}catch(PDOException $e)
11{
12  echo $e->getMessage();                         
13}

1<?php
2$servername = "localhost";
3$username = "username";
4$password = "password";
5
6try {
7  $conn = new PDO("mysql:host=$servername;dbname=myDB", $username, $password);
8  // set the PDO error mode to exception
9  $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
10  echo "Connected successfully";
11} catch(PDOException $e) {
12  echo "Connection failed: " . $e->getMessage();
13}
14?>

1$connect = new PDO("mysql:host=$host;dbname=$db", $user, $pass, array(PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION));
2