Infinite sub-catagories

[CloudedVision]

Once again, aso got me thinking. Let's say I have a database full of sentences. A sentence may be the child of another sentence, but the parent sentence may also be a child. So you have virtually infinite sub-sentences. Now how could you take that, and print it out as a list?

[darkzerox]

It's easy to represent in a database, but not so fun to parse with PHP. In the databse, you need (at least) 3 columns: sid (sentence id), pid (parent id), sentence

Each sentnece should have a unique sid. If the sentence is a root node, set pid to NULL. Otherwise, set it to it's parent's sid. "sentence" obviously stores the sentence.

Now....to parse this bugger. Off the top of my head, here's a highly inefficient algorithm:

Select all sentences with a NULL pid. For each of these, select all sentences that have a pid equal to its sid...... I hope you see where this is going. Do recursion.

[CloudedVision]

I've already got the database thing down, the PHP I'm not sure how to do. Is it possible to access my_func() from within my_func()?

[darkzerox]

Yes, that's called recursion.

Edit: Just make sure to escape when no more pid's are found or you can easily get yourself into an infinite loop.

[darkzerox]

Something like this (untested):

Code: Select all

function f($pid)
{
$result = mysql_query("SELECT * FROM sentences WHERE pid=$pid");
echo "<ul>";
while($row = mysql_fetch_assoc($result)) {
echo "<li>".$row['sentence']."</li>";
f($row['sid']);
}
echo "</ul>";
}

f('NULL');

Edit: Hey, add the code tags to the toolbar. How else am I supposed to know if these forums support them? Every forum likes to adopt their own standards >.<