mysqli_error（）不起作用

I have written a mysql_query and it is not working.

I want to know the problem via mysqli_error() however it gives the following error mysqli_error() expects parameter 1 to be mysqli

my mysql code is as follows:

$connect = mysqli_connect("localhost","root", "", "tomuman");
$query = mysqli_query($connect, "SELECT id, to FROM messages WHERE read='0'");

and mysqli_error as follows:

echo mysqli_error($query);

What could cause this problem?

You should not use $query as a parameter for mysqli_error()

use

echo mysqli_error($connect);

Just after trying to connect you can also check for specific connection errors with:

if (mysqli_connect_errno()) {
  echo mysqli_connect_error();
  exit();
}