mime_content_type
    (PHP 4 >= 4.3.0)
mime_content_type -- Detect MIME Content-type for a file
Description
string 
mime_content_type ( string filename)
     Returns the MIME content type for a file as determined by using
     information from the magic.mime file. 
     Content types are returned in MIME format, like text/plain 
     or application/octet-stream.