Mysql pdo - non-informative errorInfo

I fulfill the request:

$sql = "SELECT * FROM 'users' "; $stmt = con_pdo()->prepare("$sql"); 

I get the results:

 $rezult = $stmt->fetchAll; print_r($rezult); 

The page is clean, in table 3 entries. Trying to detect errors:

 print_r(con()->errorInfo()); 

Answer:

 Array ( [0] => 00000 [1] => [2] => ) 

I deduce

 print_r($stmt); PDOStatement Object ( [queryString] => SELECT * FROM 'users' ) 

What kind of magic?