Add fields from code

You can add any HTML you want, including any standard HTML form elements, in the form section of the CF7 interface.

In your case you could add something like:
<input type="hidden" name="my-hidden" value="hidden-value">

Yes, I understand, that in the form section of the CF7 interface I can write any HTML-code, I read doc.
But my question about using shortcode and hidden fields, beacause my hidden fields are dynamic.

And php duesn’t work in this case… why?
possible variant:
in the page-code:

<?php
....
$my_value = 'some value';
....
?>

in the forms ection:

<div style='display:none;'>
[text my_field "<?=$my_value?>"]
</div>

BUT
‘<‘ changes whis ‘htmlentities()’
what for?