Category system with PHP and MySQL

[meediake]

I want to make a script, what would make a link tree like in in windows explorer. The data is saved in MySQL database, using the following table:

ID | link_name | link_description | follow

1 | Main cat | Blah blah | 0

2 | sub cat | This is the sub. | 1

3 | Third cat. | This is third cat.| 2

This must be displayed:
Main cat
Sub cat
Third cat
etc.

Every link has its own ID and the cell "follow" shows, where does
this link belong. This system must be dynamic, i.e you can make
so many main and sub categories as you want and all this stuff can be edited in admin area.

[Dark_Storm]

I think I understand what you are talking about.
It is sort of reminiscent of a Forum, where you have a main topic, and then replies to that. The output of this is going to be different of course, but the basics are the same.
I think you may have to add another field in there, like link_type that would specify whether the row was a Main Category, a Sub Category, or just a Link. Then you execute something like the following:

$Main_query = "SELECT * FROM table WHERE link_type="Main Category";
$Sub_query = "SELECT * FROM table WHERE link_type="Sub Category";

while ($Row = mysql_fetch_array(mysql_query($Main_query)))
{
    print ("<b>Name:</b> $Row[link_name]<br><bDescription</b> $Row[link_description]");

while ($Row2 = mysql_fetch_array(mysql_query($Sub_query)))
{
     print ("<|____><b>Name:</b> $Row[link_name]<br>");
}
}

I have experimented with nested while()'s once before and it took a LOT of processing. So you may have to substitute it with for() or change your system a little so that they aren't nested.
Also when you put stuff in your follow field, you may want to input like "Self" on main categories or something. I know that I did when i made my forum, but that was a longgggg time ago and I don't remember exactly why I did it. lol so...
Hope I've been of a little help.

[meediake]

but if I want to display more sub categories.....
This has only two levels, but I want non determined number of sublevels....