pdo connection php

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$db = "mysql:host=localhost;dbname=pdolearn";
3$user = "root";
4$password = "";
5
6$pdo = new PDO($db, $user, $password);
7
8// $stmt = "SELECT * FROM countries";   //for mySQL
9$stmt = $pdo->query("SELECT * from countries");
10
11// while($row = mysqli_fetch_assoc($stmt))  //for mysql
12while ($row = $stmt->fetch())
13{
14    echo    "<pre>";
15
16    print_r($row);
17}
18

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
2class database{
3  private $host = "localhost";
4  private $db_name = "php_basic";
5  private $username = "root";
6  private $password = "";
7  private $conn;
8
9  // connect database using PDO
10  function connect_pdo(){
11    try{
12      $this->conn = new PDO("mysql:host=".$this->host.";dbname=".$this->db_name, $this->username, $this->password);
13      return $this->conn;
14    }
15    catch(PDOException $ex){
16      echo "Connection Error -->> ",$ex->getMessage();
17      echo "<br>Error Code -->> ",$ex->getCode();
18      echo "<br>Error occur in File -->> ",$ex->getFile();
19      echo "<br>Error occur on Line no -->> ",$ex->getLine();
20
21      $this->conn = null; // close connection in PDO
22    }
23  }
24}
25?>
26  
27//how to use 
28<?php
29include 'connect_db.php';
30$database=new database();
31$db = $database->connect_pdo();
32?>

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?>

1public static function connexionBDD()
2    {
3        $base = null;
4
5        try {
6            $base = new PDO('mysql:host=' . MYSQL_HOSTNAME . '; dbname=' . MYSQL_DATABASE . '', MYSQL_USERNAME, MYSQL_PASSWORD);
7        } catch (exception $e) {
8            die('Erreur ' . $e->getMessage());
9        }
10
11        return $base;
12    }