Fatal error: Cannot redeclare logged_in() (previously declared in 'abc')

<?php
include('../config.php');

if(isset($_SESSION['username']) || isset($_COOKIE['username'])){
	
	echo $_SESSION['username'];
	include('home.php');
	
}else{
	
	echo "NO";
	include('login.php');
	
}
?>

<?php
session_start();

mysql_connect('127.0.0.1','root','1234') or die (mysql_error());
mysql_select_db('lr') or die (mysql_error());
mysql_query("SET NAMES UTF8");

function logged_in(){
    if(isset($_SESSION['username']) || isset($_COOKIE['username'])){  //บรรทัดที่ 9 ที่มันแจ้งครับ
        $logged_in = TRUE;
        return $logged_in;
    }
}