By default, putting PHP tags/code in an .html document will not be processed correctly by the webserver (as the php code will actually be displayed on the html page itself when viewing it). However, the following solution will work:
Assuming you do not have access to the httpd.conf file, do the following:
1) Create a file called .htaccess
2) In this file on a single line, add the following, and save it:
AddType application/x-httpd-php .html .php .htm
3) Then upload this file into the directory with the .html files that have php in them.
If you are on a PC, you will need to name the file q.htaccess (since Windows will not allow you to save a file with only a dot as the first character). Then upload the file and rename it to .htaccess
Your .html files will now be parsed correctly for the php code.