<?php
$username = $_POST['user'];
$password = $_POST['password'];

    if($username&&$password){

//Connect to DB
       include_once("db_connect.php")or die ("Couldnt connect to DB");
//Checks whether Username exists
        $query = mysqli_query("SELECT * FROM user WHERE user='$username
        AND  password = '$password';");
        $rows = mysqli_num_rows($query);


        echo $rows;

   }else{

    echo "Please enter information";
   }
?>

$rows = mysqli_num_rows(£result);
                        ^ remove this "libra" characted and add dolar $

$rows = mysqli_num_rows($result);