How do I modify a server's files when I disable copy, unlink?

I write the php file, in which copy, unlink, Move_uploaded_files will be banned by the server;
However, there are some PHP scripts in the server that can operate correctly. Why is this?
In such an environment, how to modify the server files (ordinary files, such as JPG)?

Reply to discussion (solution)

To turn off dangerous functions:
Disable_functions = Chdir,chroot,dir,getcwd,opendir,readdir,scandir,fopen,unlink,delete,copy,mkdir, Rmdir,rename, File,file_get_contents,fputs,fwrite,chgrp,chmod,chown

If these functions are disabled in the configuration file, the functions cannot be used by the entire site, and some files are not available and some are unavailable.

The second question, if you want to rename the jpg file, and then you banned the rename function, then you can only down, the local change the name and then FTP sent up it.

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