ame Already in use in PHP Class - php

Question

I have a created db.php file for all DB configs and db related queries functions in it.
And created functions.php file and extended that db class.
And when calling any method from that functions.php file getting that error:
Fatal error: Cannot declare class db, because the name is already in
use in C:\xampp\htdocs\Final\db.php on line 3
db.php
<?php
class db{
private $host = 'localhost';
private $user = 'abc';
private $pass = 'abc123';
private $dbname = 'testphase2';
protected static $mycon;
/*
This function is to connect with DB
*/
public function dbconnect()
{
if(!isset(self::$mycon))
{
self::$mycon = new mysqli($this->host,$this->user,$this->pass,$this->dbname);
}
if(self::$mycon ==false)
{
return false;
}
return self::$mycon;
}
/*
It is used to query the database
*/
public function getrows($sql)
{
$con = $this->dbconnect();
if(!$con)
{
echo "Failed";
}
else
{
//echo "Connected";
$result = mysqli_query($con,$sql) or die(mysqli_error());
}
return $result;
}
/*
It is used to query and fetch the dataset into array and return from the database
*/
public function fetchrows($query)
{
$rows = array();
$result = $this->getrows($query);
if($result== false)
{
return false;
}
while($row = $result->fetch_assoc())
{
$rows[]= $row;
}
return $rows;
}
public function db_close(){
mysqli_close($this->$mycon);
echo "Connection closed";
}
}
?>
functions.php
<?php
require('db.php');
class functions extends db{
public $currendata = '';
public function fetch_current_Record($id)
{
$con = new db();
$show_existingdata = "Select word from dictionary where id=$id";
$currendata = $con->fetchrows($show_existingdata);
return $currendata;
}
public function get_language()
{
try{
$con = new db();
$query = "SELECT language_id from language";
$result = $con->fetchrows($query);
return $result;
}
catch (Exception $e)
{
echo "Exception MESSAGE: ".$e->getMessage();
}
}
}
?>