Ensure that you're sending a Content-type header telling it the page is in UTF-8.
In any case you should not use UTF-8 with PHP because it doesn't understand it.
None of the PHP string handling is written to deal with unicode / UTF8 correctly, so in general it will corrupt UTF8 strings.
If you need to use UTF8 for your web site, I STRONGLY RECOMMEND that you don't use PHP. Its designers were just entirely ignorant of any encoding issues whatsoever, and assumed the entire world used 8bit character sets.
Mark