Aviso: mysqli_fetch_all () espera que o parâmetro 1 seja mysqli_result, bool dado em c: newxammp htdocs learn index.php na linha 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
Nagraj!