search files in directory using php

[DirtyPlaya]

i have a situation,i am creating a folder everytime when new user register.the folder name is equal to username.so therefore user_data folder contains all folder which name is equal to username.when user upload something then it directly save to its desired username folder.so now i want to search perticular file from these folder. i know that, that particular file save in user_data folder but i dont know in user_data foder which folder contain that file.so what will be the code for searching file in directory.