php / Mysql best tree structure

I have to build a tree that will contain about 300 nodes inside it. The tree has no depth limitations. So it can have 3 or 15 levels. Each node can have an unlimited number of children.

The priority is to get a complete tree / subtree the faster as possible, but I also need to add nodes or move nodes sometimes but not that often.

I want to know the best way to store the tree in the database and the best way to retrieve the data, if possible, in php.