fairly simple question and I haven’t seen anything asked with this exact scenario laid out.
I have a form on a page. “Page 1”
The form’s action is calling a PHP document, and the target is set to _blank. “Page 2”
The PHP document processes the information, then sets the header info to a specific page. “Action 1”
I would like for “Action 1” to instead open multiple pages; I know of several ways to do this via javascript, however, I would like to stay entirely within the PHP file if at all possible.
As php is a server-side language and HTTP has (thankfully) no way of redirecting to multiple URLs, you’ll need to implement your feature in JavaScript. Note that this is extremely likely to fail on mobile and exotic user agents, and it’s a hassle to users in any case.