Temporary storage of data

Hello, all - I am building a script that basically records some data on the local server for a period of about one hour. At that time, the data is sent to another server by means of HTTP POST. The problem I'm faced with is how to store the data locally. There are a few things that we're going to have to assume, due to options that are not under my control: Solution has to rely on internal PHP functions, i.e. nothing compiled into PHP (I was hoping a DMB-style database would be good, but cannot be used since it has to be compiled into PHP) Solution has to store data in a public place, i.e. /tmp/somedata/, as the person using the script may not have access to change permissions. I would like to store data in a public folder, but would also like for this data to be encoded somehow. serialize()'d data can still be visually decoded, else I'd use that, as well. Solution cannot assume that MySQL, PGSQL, or any other database application is available to use. I guess the problem is, how would one go about making multiple secured read/writes to a file, such as a mini-database, without relying on any options that are compiled into PHP? We're talking on a bare-bones vanilla PHP installation, with no DBM, MySQL, PGSQL, dbm, or otherwise "real" database support in it. Any input on this would be very greatly appreciated. Thanks -dant