Question about SQL and Graph nodel trees

I cannot be the only one that is having this problem, what are you using for DAG (Direct Acrylic Graph)? I need to have a mesh node edge graph and am having trouble with this? I see that Neo4j has a rest server and I can do this in Java but I want to do it in PHP with a MYSQL or postgresql. If you are doing something like this, can you please tell me how you are doing this. I can do a relationship with a parent child or a nested tree, but I need to do a DAG. Thanks for the help, timgerr