Php Code: Parent , Child Category Tree

This is a simple PHP script to generate a Category Tree structure based on parent/child MySQL database. Database structure looks like this:

- category_id
- parent_id
- title

And will generate a structure like this:

Category 1
- Sub Category
- Sub, Sub Category
- Sub Category 2
Category 2

This is much simpler and works very well. The other code I found on this forum didn't work at all and was very complicated, so I wrote an easy script. Just 1 note: It's meant for a structure that does not have a root element.

<!-- This Script is from www.hawkee.com, found at www.phpfreecode.com--><br /><b>Warning</b>: mysql_query() [<a href='function.mysql-query'>function.mysql-query</a>]: Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (2) in <b>/home/content/k/k/r/kkr152/html/phpfreecode/parent_child_category_tree.htm</b> on line <b>175</b><br /><br /><b>Warning</b>: mysql_query() [<a href='function.mysql-query'>function.mysql-query</a>]: A link to the server could not be established in <b>/home/content/k/k/r/kkr152/html/phpfreecode/parent_child_category_tree.htm</b> on line <b>175</b><br /><br /><b>Warning</b>: mysql_fetch_array(): supplied argument is not a valid MySQL result resource in <b>/home/content/k/k/r/kkr152/html/phpfreecode/parent_child_category_tree.htm</b> on line <b>182</b><br /><br><font face="Tahoma"><a target="_blank" href="http://www.phpfreecode.com/"><span style="font-size: 8pt; text-decoration: none">PHP Free Code</span></a></font>