Unanswered: Call to undefined method DateTime::add()
please, help me with the date addition. I saw some threads dealing similar topics, but I still don't understan why is the method undefined. I try both forms: DateTime::add() method as well as date_add() function. PHP function reference says this should work.. And I have very same problem with sub() method.
$eventStart = new DateTime( "2009-02-13 20:00:00" );
$eventStart->add( "P7D" ); ... error message in subject.