ciao
risolto in questa maniera

codice:
if($extrab !=0 || $extrac !=0) {
    if ($ora>="20:00" && $ora<="24:00"){
    $ritornocompleto.="<tr><td>"._EXTRA.":</td><td><b>$extrab euro</b></td></tr>";
        } 
    else if($ora<="07:00"){
        $ritornocompleto.="<tr><td>"._EXTRA.":</td><td><b>$extrac euro</b></td></tr>";
         } 
     
    if ($ora2>="20:00" && $ora2<="24:00"){    
    $ritornocompleto.="<tr><td>"._EXTRA.":</td><td><b>$extrab euro</b></td></tr>";
        } 
    else if($ora2<="07:00"){        
        $ritornocompleto.="<tr><td>"._EXTRA.":</td><td><b>$extrac euro</b></td></tr>";
         } 
    

}