当我尝试将信息输入数据库时​​收到此消息

This is my error:

Fatal error: Uncaught Error:
  Function name must be a string in /home/kmsrutge/public_html/Login2process.php:5
Stack trace:
  #0 {main} thrown in /home/kmsrutge/public_html/Login2process.php on line 5

My code:

    $db_server = $mysqli_connect($db_hostname, $db_username, $db_password);
    if (!$db_server) die("Unable to connect to MySQL: " . $mysqli_error());

    $mysqli_select_db($db_database) or die("Unable to select database: " . $mysqli_error());


    $sql = "UPDATE Invoices SET Ord_ID = '$9144' WHERE Prod_ID = '98'; ";

    $result = $mysqli_query($sql);


    if($result) echo "UPDATE success!"; else echo "UPDATE failed!";


    if($result)
    {

        echo "<p>New row was successfully inserted</p>".
        $insertQueryCount = $insertQueryCount+1;
    }
    else
    {
        echo "<p>Your insert failed.</p>";
        die($mysqli_error());
    }
?>

I read that it may be a possible PHP 7 issue. Any idea on how to correct this?

Try changing the result variable to the following:

     $result = mysqli_query($db_server, $sql);

Please check your code SQL function do not start with $ so you got the error. remove all $ from mysqli.

Please change the first line:

$db_server = mysqli_connect($db_hostname, $db_username, $db_password,$db_database);

you don't require mysqli_select_db function so comment that line and check.

Also the fifth line change like mysqli_query($db_server,$sql).

Please read (https://www.w3schools.com/php/php_mysql_intro.asp)this documents how to connect SQL and how to write a query.