PHP Dynamic Tabindex Numeration

Hello,
it’s since long time that I try to get a PHP Dynamic Tabindex Numeration for every links and inputs, in a theme; but I don’t find the right way to do it.
I’m using
<?php $t = 1; ?>
in the header.php, then add
tabindex=”<?php echo $t++ ?>”
and/or
tabindex=”‘. $t++ .'”
in all links and input fields.
It will looks like in this test post https://obertfsp.com/wordpress/2009/01/10/xampp_on_windowsxp/
somewhere the tabindex value isn’t printed at all,somewhere I get two 1..it’s all done so randomly, and I don’t find where I’m doing wrong.
Usually,in a php standalone page, it will works correctly, not in a wp theme.
I would be glad to find a definately way.

Thanks.
Alberto