Recursive SQL Expression?

Hi folks... I've a small problem working out the best method of reading data from a mySQL database with PHP... The table is a simple self-referential table constructed (loosely) as follows:

cat_id      integer  unique
cat_name    string

cat_parent integer (points to a cat_id or 0 if no parent). Now, I need to extract the data in 'tree order', that is each cat (catgory) with it's siblings then the next category and so on... I'm currently forced into using a very nasty bit of code to list each category within a particular category - this is fine for a small dataset, but a large one results in a rather expensive load on the database server. Anyone got any bright ideas, 'cos I'm stumped. Assuming the following data: cat_id cat_name cat_parent

1        SF         0
2        PH         0
3        FO         2
4        BB         1

the sql statement should return a dataset like: cat_id cat_name cat_parent

2        PH         0
4        BB         2
1        SF         0
3        FO         1

Notice that category names are in order. This produces the tree-like structure +--PH | +--BB +--SF +--FO Thanks for any help... -- Alan