php how to connect to db using pdo

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<?php 
2  
3	$pdo = new PDO('mysql:host=localhost;
4  				dbname=the_name_of_your_databe,
5  				'username', 
6                'password'');
7# by default your username is root 
8# if you don't have a password don't fill in it
9
10#(optional) : 
11	$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
12	$pdo->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_OBJ);
13
14?>

1<?php 
2  $db_src    = "mysql:host=localhost;dbname=databasename";
3  $db_user   = "root";
4  $db_pass   = "";
5  try{
6    $connect = new PDO($db_src, $db_user, $db_pass);
7    $connect->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
8  }
9  catch(PDOEXCEPTION $err){
10    echo "Failed To Connect. Error " . $err->getMessage();
11  }
12/* Variable $connect will be used to execute DB Statements*/

1$db = new PDO("sqlsrv:Server=YouAddress;Database=YourDatabase", "Username", "Password");
2