Prevent subdomain access to parent folder?

For example: I have "abc.com" and i use "cpanel" In "cpanel -> Domains -> Subdomains" i create Subdomain: "x.abc.com" Document Root: "/home/abc/public_html/hisfolder" And i will give this address to my customer i don't want he access to my other files except "hisfolder" He must only access with "ftp" to "hisfolder" and my Database. And i create In "cpanel -> Files -> Ftp Accounts" Login: "hisname@abc.com" Password: "*****" Directory: "/home/abc/public_html/hisfolder" With "filezilla" or etc. he only access "hisfolder" he can't access to parent folders and files OK. But when he write a ".php" file like: and upload to "/home/abc/public_html/hisfolder/index.php" he can now access to my files?

• He should add his .php files and connect to database
• He should not access to my files

So how can i do this both agents? what am i do? Please Help me.