Calling file from a form

[MasterDucky]

When you call a .php file from a html form is there a way to not open a
new window just execute the file?

<form action=guess.php method=post >
        <input type="text"  id="film" name="film"><br><br>
        <input type="submit" name="theinput" value="Check!">
    </form> 

I want to call a popup window from guess.php if the condition is true, tested in guess.php, but i dont want guess.php to open a new window.

I tried the 'target=' method but it didnt work and they say it's depricated too.