PHP in UTF8 and utf-8

I believe a lot of programmers will have this kind of doubt at first, title, I also.
In fact, they can be distinguished by this.
First, in PHP and HTML set code, please try to write "UTF-8", this is the standard notation, and Utf-8 is only in the window is not a case-sensitive way of writing, and secondly, most of the cases are written "UTF8" or "UTF8" program can also be recognized, But in IE browser does not recognize it, so, best, strictly written "UTF-8", such as:
<?php header (' content-type:text/html; Charset=utf-8 ');?>
<meta http-equiv= "Content-type" content= "text/html; charset=utf-8" />
Second, in the database Setup code, must be written as "UTF8", because the MySQL command mode can only identify "UTF8", do not recognize "utf-8", such as: PHP program can write:
<?php mysql_set_charset (' UTF8 ', $link); ?>

PHP in UTF8 and utf-8