PDF_create_action()

(PECL pdflib >= 2.0.0)

Create action for objects or events

说明

PDF_create_action(resource $pdfdoc,string $type,string $optlist): int

Creates an action which can be applied to various objects and events.

Here is a note i feel important for newbies
$url = PDF_create_action($p, "URI", "url=http://www.pdflib.com");
PDF_create_annotation ($p, 44, 100, 55,700, "Link", "linewidth=0 action {activate $url}");
Above 2 lines will change the hand
cursor once your cursor is in the rectangle as assigned by the
create_annotation command. Once you click in that area, it will
bring you to the url in create_action command.

The equal sign is interpreted as a separator sign in the optlist. But there's a way to have an url with GET params.
With the example given below:
$url = PDF_create_action($p, "URI", "url {http://www.pdflib.com/?page=home}");
PDF_create_annotation ($p, 44, 100, 55,700, "Link", "linewidth=0 action {activate $url}");

I just want to point out that PDF_create_action does not work for URLs with GET parameters (has problems with '='). Running urlencode will just create a URL that is not translated properly by the browser (at least for Firefox 2.0.0.11).
Believe it or not, your best bet is to use pdf_add_weblink(), which is supposedly deprecated.