public function shift($_time, $_startIndex = null, $_endIndex = null)
{
if (!is_int($_time)) {
return false;
}
if ($_time == 0) {
return true;
}
if (null === $_startIndex) {
$_startIndex = 0;
}
if (null === $_endIndex) {
$_endIndex = $this->getCuesCount() - 1;
}
$startCue = $this->getCue($_startIndex);
$endCue = $this->getCue($_endIndex);
//check subtitles do exist
if (!$startCue || !$endCue) {
return false;
}
for ($i = $_startIndex; $i <= $_endIndex; $i++) {
$cue = $this->getCue($i);
$cue->shift($_time);
}
return true;
}