How to pass an IFRAME SESSION to the parent page?

Is it possible to pass a SESSI开发者_高级运维ON variable from am embedded IFRAME to the parent page?

Meaning:

<form>

<iframe>
upload image to fake AJAX.
With PHP, set $_SESSION to be the location of the temporary uploaded photo
</iframe>

<input type="submit" />  // will this form submit have the $_SESSION variable set from the IFRAME?

</form>

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PHP sessions are, by default, implemented using cookies (which are per-domain).

You don't need to do anything explicit to share them between different frames (except keep them on the same domain).