pdo - Equal in select does not work as expected -

i found funny behaviour using equal pdo. checked several select-statements in phpmyadmin , pdo , results vary. has idea whats wrong?

$sql = "select * fenster fenster > 'news'";  //works ok $sql = "select * fenster fenster < 'news'";  //works ok $sql = "select * fenster fenster <= 'news'";  //works ok  $sql = "select * fenster fenster >= 'news'";  // news not in result $sql = "select * fenster fenster = 'news'";   // news not in result  $stmt = $db->prepare($sql);  $stmt->execute(); 

$feldname = array_keys($stmt->fetch(pdo::fetch_assoc));

while($data = $stmt->fetch()) {     var_dump($data); } 

i found reason myself. $feldname = array_keys($stmt->fetch(pdo::fetch_assoc)); did read missing row, did not show afterwards. have find workaround.