(PECL ps >= 1.1.0)
ps_open_file — Opens a file for output
Creates a new file on disk and writes the PostScript document into it. The file will be closed when ps_close() is called.
Resource identifier of the postscript file as returned by ps_new().
The name of the postscript file. If filename is not passed the document will be created in memory and all output will go straight to the browser.
成功时返回 TRUE, 或者在失败时返回 FALSE.