Standalone PHP script not working when fired from referring

Hi guys, I wonder wether anyone came accross this problem:

The standalone script _samples/php/standalone.php works just fine when called directly, however when you call it from refferring page via javascript

window.open(standalone.php)

or from href link via

<a href="standalone.php" target=_blank>select image</a>

it shows the finder but after selection (double click) it doesn't execute the SelectFunction (default ShowFileInfo()). Instead it just closes the new window and returns focus to the parent/opener page.

Anyone knows why it is so and how can I prevent this?

FYI: What I want to do is simply return the fileUrl value to one of the referring page's (opener's) form fields. I believe I should be able to pass the value within the ShowFileInfo function like this

opener.forms["myformname"].myfieldname.value = fileUrl; 

Thanks for your hints