Warning: mysqli_fetch_all() expects parameter 1 to be mysqli_result, bool given in C:\newxammp\htdocs\learn\index.php on line 11

#where you are running mysqli_query , add 'or die( mysqli_error($db)'
#e.g
$sql = "SELECT * FROM users";
$result = mysqli_query($db, $sql) or die( mysqli_error($db));
#$db being the variable holding the connection to db