Just to clarify:
 - are you using PHP 7.2.25 or 7.2.24?
 - which driver do you use – mysqlnd or libmysqlclient?

1. use 7.2.24 

2. use mysqlnd 5.0.12-dev - 20150407 - $Id: 3591daad22de08524295e1bd073aceeff11e6579 $ 
($connectionID->get_client_info();)
Package: php7.2-mysql 
Version: 7.2.24-1+ubuntu18.04.1+deb.sury.org+1
Provides: php-mysqli, php-mysqlnd, php-pdo-mysql, php7.2-mysqli, php7.2-mysqlnd, php7.2-pdo-mysql

Thanks!

I think you have something going on with the your function.  you need to sense if it exists, and the connection scheme is installed (if you are looking for deployment) Try:

a fixed version of the Procedure style in a function (which I would not recommend):

function connect(){
if(!isset($connectionID)){
$connectionID = mysqli_init();
if (!$connectionID){die("mysqli_init failed");}
 
mysqli_real_connect($connectionID,'localhost', 'dbuser', 'dbpass', 'dbscheme');
}}


connect();


But you shouldn't use a connect in a function ever!
 You should always control the connection state, and close the connection at the end of page.... use "require" call then   mysqli_close($con); at the end of working with the database, in your php page.
But If you need to call a connection, within a page, I recommend checking it first:

if(!isset($connectionID)){
$connectionID = mysqli_init();
$con= mysqli_real_connect($connectionID,'localhost', 'dbuser', 'dbpass', 'dbscheme');
}

Here is an object oriented version:

$mysqli = mysqli_init();
if (!$mysqli) {die("mysqli_init failed");}
$con -> real_connect("localhost","dbuser","dbpass","my_db");



Just remember to  use the procedural: mysqli_close($con); or the object oriented: $mysqli -> close(); to close the connection at the bottom of your php page.

> Just remember to  use the procedural: mysqli_close($con); 
> or the object oriented: $mysqli -> close(); to close the 
> connection at the bottom of your php page

please stop to educate closing mysql connections!

PHP does it at it's own at the end of the request when it#s not a persistent connection and if you ever decide to use persistent connections by 'p:localhost' instead 'localhost' you will regret your mysqli_close() which is less smart than PHP

To drtechno at mail dot com.
Please read the contents carefully before commenting. It is a persist connection and errors that occur when using it. I wrote a simple example of how to repeat the error, as required by the bug report tracker. If it’s convenient for someone, you can skip connect(); 2 times, but in this case you will need to reload the page 2 times. Don't like a function call? write without a function, the meaning will not change. Please do not write nonsense if you do not understand the topic. Good luck.

This connection style is used in the ADODB library.
https://github.com/ADOdb/ADOdb/blob/master/drivers/adodb-mysqli.inc.php
function _connect() lines 89-144 in current master branch.