Can anybody explain why this accented character routine works?

For a while I had been needing a process to allow French-speaking
users to send text, including accented characters, to the server via
AJAX. These characters would then be left as normal accented
characters, ready to be written to a text file, or prepared for HTML
files as HTML entities.

I found a way to do it by trial and error, and it works beautifully.
Trouble is, I am writing an AJAX manual and I am supposed to guide
readers on this process - but I can't really explain why it works, as
it is not particularly intuitive. Can anybody help?

The HTML file has a meta tag in the header with the following:

content="text/html;charset=utf-8"

The Javascript sends the text after delimiting it as follows:

escape($t);

In the PHP file the following serious of functions is applied:

$t=utf8_encode($t);
$t=utf8_decode($t);
$t=stripslashes($t);

After being encoded and decoded again the accented characters come
through brilliantly. I can then either write to a text file or prepare
the text for an HTML file as follows:

$t=htmlentities($t);

The thing I do not understand is why the need to encode and then
decode?

I would be very grateful if somebody could throw some light on this.

Thanks for you time,

Max