PHP5 to PHP7 DatabaseConnection

I am look at an old PHP project that uses mysql_connect, and I am trying to update it to PHP 7, by using mysqli_connect.

In the original project, I had a file - connect.php which had the database info, I would then include that file where needed.  But I cant seem to get this to work in PHP7

Original file looked like this.

 <?php
// Connects to my Database
mysql_connect("your.hostaddress.com", "username", "password") or die(mysql_error());
mysql_select_db("Database_Name") or die(mysql_error());
?>

I have changed to this

<?php

$con=mysqli_connect("your.hostaddress.com", "username", "password","Database_Name");

?>

now on  a page where I had

return mysql_real_escape_string($data);

and am now trying to use

return mysqli_real_escape_string($con, $data);

and I get the error con is not defined.

How can i keep the original structure but update to PHP7