Trouble with checking mysqli_fetch_assoc results - php

Question

I'm having an issue on a personal project. I'm creating a project board where a user can log in, create different projects and add tasks to them. Basically a categorised to do list.
When the user logs in they are redirected to a screen that lists their already created boards. If no boards have been created then a link to "create board" will be displayed
When the user logs in their user name is saved in a session and called with $username
I have two tables, user and boards:
USER:
+---------+----------+-----------------+------------+
| user_id | username | email | password |
+---------+----------+-----------------+------------+
| 1 | user1 | user#user1.com | pass1 |
| 2 | user2 | user#user2.com | pass2 |
| 3 | user3 | user#user3.com | pass3 |
+---------+----------+-----------------+------------+
BOARDS:
+----------+-----------------+---------+
| board_id | board_name | user_id |
+----------+-----------------+---------+
| 1 | user1-board1 | 1 |
| 2 | user1-board2 | 1 |
| 3 | user2-board1 | 2 |
| 4 | user2-board2 | 2 |
+----------+-----------------+---------+
Note user 3 hasn't created any boards.
I run the below query to pull all associated boards for the current logged in user and display the board name.
$query = "SELECT board_id, board_name, boards.user_id, username ";
$query .= "FROM boards, user ";
$query .= "WHERE boards.user_id = user.user_id ";
$query .= "AND user.username = '{$username}' ";
$set = mysqli_query($connection, $query);
This all works fine and when I run the below code I can display the board names.
while ($boards = mysqli_fetch_assoc($set)) {
echo $boards['board_name'];
echo "<hr/>";
}
The problem I am having is displaying a "create board link" when a user is logged in but hasn't created any boards. I.e user 3.
My code:
if (!mysqli_fetch_row($set)) {
echo "create board";
} else {
while ($boards = mysqli_fetch_assoc($set)) {
echo $boards['board_name'];
echo "<hr/>";
}
}
I have tried variations of the above code but this is the closet i've got. If user 3 (who has no boards) logs in, he is greeted with "create board" so I presume it works as there are no rows of data associated with that user. However, if user 1 logs in (has 2 boards) only the second board name is being displayed. If I remove the !mysqli_fetch_row code then both board names are outputted. Obviously the fetch_row is effecting the results but I can't work out why.
If anyone can offer any guidance in how to check if a user has any boards I would be very grateful. Also if anyone can explain (for my own personal development) why running fetch_row alters my result set that is passed to the while loop it would be a bonus.
Thanks in advance

Answer 1

This line:
if (!mysqli_fetch_row($set)) {
both fetches and consumes a row from the result set. Since you're not assigning that returned row to a variable, it's utterly lost. If there are rows found, you then go off to the else clause, now missing one row of results.
You need to check how many rows were found, THEN start consuming:
if (mysqli_num_rows($set) == 0) {
... there are no rows ...
} else {
... there are rows: loop and display them
}