Hmmm. I ran this script to test it (it looked fine to me you see):
<?
$str = "\"Hello\"";
$str = ereg_replace("\"","'",$str);
echo $str;
?>
and it output:
'Hello'
as required. The only other thing to try, which should do the same thing is:
$str = ereg_replace('"',"'",$str);
All the best,
Louis