mysql connect getting deprecated error

Question

I'm getting a deprecated error with the following code

require 'dbconfig.php';
function checkuser($fuid,$ffname,$femail){
        $check = mysql_query("select * from Users where Fuid='$fuid'");
    $check = mysql_num_rows($check);
    if (empty($check)) { // if new user . Insert a new record       
    $query = "INSERT INTO Users (Fuid,Ffname,Femail) VALUES ('$fuid','$ffname','$femail')";
    mysql_query($query);    
    } else {   // If Returned user . update the user record     
    $query = "UPDATE Users SET Ffname='$ffname', Femail='$femail' where Fuid='$fuid'";
    mysql_query($query);
    }
}

but every time I try to use mysqli I get a error

Warning: Cannot modify header information - headers already sent by

what should I do?

Answer 1

Warning. This extension was deprecated in PHP 5.5.0, and it was removed in PHP 7.0.0. Instead, the MySQLi or PDO_MySQL extension should be used. See also MySQL: choosing an API guide and related FAQ for more information. Alternatives to this function include:

mysqli_connect() PDO::__construct()

http://php.net/manual/en/function.mysql-connect.php

Cannot modify header information - This error has nothing to do with databases.