how to determine the mime type of a general blob?

i've perused the general PHP site and the PEAR site, and i haven't found anything that will let me determine the mime type of a simple blob of bytes. everything seems to be based off of the data being in a *file*. in my case, it's not in a file, it's simply a stream of bytes in a variable, and i'd rather not have to write all that data to a file just to identify its mime type. surely there's something that will tell me the mime type of a string of bytes, no? rday -- ======================================================================== Robert P. J. Day Waterloo, Ontario, CANADA Linux Consulting, Training and Kernel Pedantry. Web page: http://crashcourse.ca Twitter: http://twitter.com/rpjday ========================================================================