Insert into database in OOP doesn't work - php

Question

I'm trying to make object oriented login and insert into database, following tutorial but this doesn't work. It won't make connection to database, error: No database selected. Can you help me?
This is code:
form in index.php
<form action="insert.php" method="post">
Firstname: <input type="text" name="fname" /><br><br>
Lastname: <input type="text" name="lname" /><br><br>
<input type="submit" />
Class in insert_class.php:
<?php
class Insert_class {
public $servername;
public $username;
public $password;
public $dbname;
public function __construct(){
// Create connection
$conn = mysqli_connect($servername, $username, $password, $dbname);
// Check connection
if (!$conn) {
die("Connection failed: " . mysqli_connect_error());
}
// insert into database
$sql = "INSERT INTO nametable (firstname, lastname)
VALUES ('$_POST[fname]','$_POST[lname]')";
if (mysqli_query($conn, $sql)) {
echo "New record created successfully";
} else {
echo "Error: " . $sql . "<br>" . mysqli_error($conn);
}
mysqli_close($conn);
}
}
Object for login and insert in database in insert.php:
require 'insert_class.php';
$insert = new Insert_class();
$insert->servername ='localhost';
$insert->username ='root';
$insert->password ='';
$insert->dbname ='newdatabase';

Answer 1

Try this
<?php
class Insert_class {
private $servername;
private $username;
private $password;
private $dbname;
private $con
public function __construct($servername,$username,$password,$dbname)
{
$this->servername = $servername;
$this->username = $username;
$this->password = $password;
$this->dbname = $dbname;
// Create connection
$this->conn = mysqli_connect($this->servername, $this->username,
$this->password, $this->dbname);
if ($this->con->connect_error) {
die('Connect Error (' . $this->con->connect_errno . ') '. $this->con->connect_error);
}
// etc
}
Then you can do
require 'insert_class.php';
$insert = new Insert_class('localhost','root','','newdatabase');
Notice I also captured the $con as a property. Your code would have lots it as it would only have been visible in __construct but none of the other methods you may want to write in this class.
Also Notice I changed the test for a successful connection. This is the correct way to check if a connection was successful. a simple if( ! $con ) is not good enough.

Answer 2

Rather than defining the connection details explicitly ,you can use DEFINE ..
define("DB_HOST", "localhost");
define("DB_USER", "root");
define("DB_PASSWORD", "");
define("DB_NAME", "newdatabase");
insert_class.php ...
public function __construct(){
$conn = mysql_connect(DB_HOST,DB_USER,DB_PASSWORD) or die(mysql_error());
mysql_select_db(DB_NAME, $conn) or die(mysql_error());
}