致命错误：在null上调用成员函数connect（）

Question

Trying to include function "overlay" from config.php into other php pages.

Index.php:

<?php include("./config/config.php");
over_lay(); ?>
//// html code ////

The error is:

Fatal error: Call to a member function connect() on null in ...\config\config.php on line 182

Part of config.php:

include("./config/mysql.php");
function over_lay()
{
$mysqli->connect();
?>
//// html code with partly mysqli requests ////
<?php
  $mysqli->close();
}
?>

And finally mysql.php:

<?php
function connect() 
{
$mysqli = new mysqli("localhost","root","","database_name");
$mysqli->query("SET NAMES utf8");
return $mysqli;
}
?>

I'm testing this on OpenServer and of course I do have the database.

Answer 1

Call the function inside your over_lay

include("./config/mysql.php");
function over_lay()
{
    $mysqli = connect();
     ?>
     //// html code with partly mysqli requests ////
     <?php
     $mysqli->close();
 }

Update I simply changed

$mysqli->connect();

to

$mysqli = connect();