database connection in php

1<?php
2$servername = "localhost";
3$username = "username";
4$password = "password";
5$dbname = "myDB";
6
7// Create connection
8$conn= mysqli_connect($servername,$username,$password,$dbname);
9// Check connection
10if (!$conn) {
11  die("Connection failed: " . mysqli_connect_error());
12}
13echo "Connected Successfully.";
14?>

1<?php
2
3$hostName = 'localhost';
4$userNmame = 'root';
5$password = '';
6$dbname = 'topproduct';
7$db_name = "mysql:host=$hostName;dbname=$dbname";
8$conn = new PDO($db_name,$userNmame,$password);
9
10if(!$conn){
11    echo 'Error database connection';    
12}
13

1<?php
2///////////neha jaiswal/////
3/////set variable/////////
4$serve="localhost";
5$user="root";
6$password="";
7$db="cart_system";///database name
8///create connection with db////
9$conn=mysqli_connect($serve,$user,$password,$db);
10////check condition for connection fail or not
11 if ($conn) {
12 echo "connection success"; 
13 }else
14{echo "connection unsuccess"; 
15 }
16  ?>

1Just include this Temlate in other file using PHP Include/Require Keywords
2 And Make Connection In One Shot :)
3
4<?php
5  
6    // echo "Welcome to Connecting of DB Tutorial!";
7    // echo "<br>";
8
9    // 1. PDO - Php Data Objects
10    // 2. MySQLi extension
11
12    // Set Connection Variable
13    $server = "localhost";
14    $username = "root";
15    $password = "";
16    $database = "test";
17
18    // Create A Connection
19    $con = mysqLi_connect($server, $username, $password, $database);
20
21     // Check For Connection
22     if(!$con){
23        die ("Connection Terminated! by Die() function". mysqLi_connect_error());
24       
25    }
26    else {
27        echo "Connection Succefully Happened! <br>";
28    }
29
30
31    ?>

1<?php
2$servername = "localhost";
3$username = "username";
4$password = "password";
5
6// Create connection
7$conn = new mysqli($servername, $username, $password);
8
9// Check connection
10if ($conn->connect_error) {
11    die("Connection failed: " . $conn->connect_error);
12}
13echo "Connected successfully";
14?>

1<?php
2$servername = "localhost";
3$username = "yourusername"; // For MYSQL the predifined username is root
4$password = "yourpassword"; // For MYSQL the predifined password is " "(blank)
5
6// Create connection
7$conn = new mysqli($servername, $username, $password);
8
9 
10// Check connection
11
12 if ($conn->connect_error) {
13
14    die("Connection failed: " . $conn->connect_error);
15}
16
17echo "Connected successfully";
18
19?>