(PECL ps >= 1.1.0)
ps_close — Closes a PostScript document
$psdoc): boolCloses the PostScript document.
This function writes the trailer of the PostScript document. It also writes the bookmark tree. ps_close() does not free any resources, which is done by ps_delete().
This function is also called by ps_delete() if it has not been called before.
成功时返回 true， 或者在失败时返回 false。