Zipping all files and folders without php exec

Question

I am looking to a way to zip all my files and folders for a project i am working on i have everything working with the code below on my install.

exec('tar -czf backup.tar root/');

But on the clients shared hosting we get the error.

Warning: exec() has been disabled for security reasons in 

Can anyone suggest the best way to do this without exec function???

Would really help thanks.