As an effort to remove those Word copy and paste smart quotes, I've found that this works with UTF8 encoded strings (where $text in the following example is UTF8). Also the elipsis and em and en dashes are replaced.
There is an "invisible" character after the †for the right side double smart quote that doesn't seem to display here. It is chr(157).
<?php
$find[] = '“'; $find[] = 'â€'; $find[] = '‘'; $find[] = '’'; $find[] = '…'; $find[] = '—'; $find[] = '–'; $replace[] = '"';
$replace[] = '"';
$replace[] = "'";
$replace[] = "'";
$replace[] = "...";
$replace[] = "-";
$replace[] = "-";
$text = str_replace($find, $replace, $text);
?>