How can I open a pdf file?

[nomo1994]

I need to write a simple PHP code that has a text link.

When a user clicks the text link, a pdf file should open inside the browser.

One of the requirments is that a url should not change.

So, for example, you start with index.php. When you click the text link and open a pdf file, a url should remains the same, which is index.php.

 

I have an idea of using a POST parameter, but I do not know exactly how I can achieve this.

Any help is appreciated.