(PECL ps >= 1.1.0)
ps_delete — Deletes all resources of a PostScript document
$psdoc): boolMainly frees memory used by the document. Also closes a file, if it was not closed before with ps_close(). You should in any case close the file with ps_close() before, because ps_close() not just closes the file but also outputs a trailor containing PostScript comments like the number of pages in the document and adding the bookmark hierarchy.
成功时返回 true， 或者在失败时返回 false。