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"

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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.