为什么我无法使用php在amazon ec2服务器上传超过3 MB的文件？

I am working with Amazon EC2 server with linux instance. In my project user can upload video. So I used php to upload the file. It is working in other server but not working in amazon ec2 server. When I upload file less than 1 mb it is working but if the file size is greater than 3mb than it is not working.I don't know where to set the permission to upload large file. What can I do?I am working with Amazon EC2 server with linux