Deleting array index, how?

Hi,

I have an array:

$sentences = array("1","2","3","4");

How can I delete an index or indexes? I don't want to leave empty stringed array indexes...

Thank you!

This:

// Now delete every item, but leave the array itself intact:
foreach ($sentences as $i => $value) {
unset($sentences[$i]);
}

Comes from this site:
http://us2.php.net/types.array