I can only give you the theory of how I did it. This isn't because I don't want to share it, but it has too many dependencies. What I did was the following:

1. Generate a random number using PHP. Select from the table where the ID is more or equal to;
2. Add that selected ID to an array and execute the first query;
3. When we loop again, follow the same process but append IN() to the end with the previously selected IDs;
4. Keep doing this until we get the amount we require.

As this is selecting an ID, which should be the primary key, it is a much faster select than choosing a random line from the database.

__________________
The man who comes back through the Door in the Wall will never be quite the same as the man who went out.