how to connect with db in php code example

Example 1: php sql connection

<?php
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

// Create connection
$conn= mysqli_connect($servername,$username,$password,$dbname);
// Check connection
if (!$conn) {
  die("Connection failed: " . mysqli_connect_error());
}
echo "Connected Successfully.";
?>

Example 2: php sql server connect

$serverName = "serverName\sqlexpress"; //serverName\instanceName
$connectionInfo = array( "Database"=>"dbName", "UID"=>"userName", "PWD"=>"password");
$conn = sqlsrv_connect( $serverName, $connectionInfo);

Example 3: database connection in php

<?php

$hostName = 'localhost';
$userNmame = 'root';
$password = '';
$dbname = 'topproduct';
$db_name = "mysql:host=$hostName;dbname=$dbname";
$conn = new PDO($db_name,$userNmame,$password);

if(!$conn){
    echo 'Error database connection';    
}