Current I am using the official Asana PHP API to query all the projects that belong to one specific workspace. Then, for each project I query all the tasks. That works but takes a lot of time as there is one request per project to get the tasks.
First I call $client->projects->findByWorkspace that internally uses /workspaces/workspace-id/projects and then for each project
Then I call $client->tasks->findByProject($project->id); that internally uses /projects/project-id/tasks
I have been playing with expand, fields, opt_fields but I can’t get all the tasks included in the first call. I hope the API supports this.