如何在某些特定页面中禁用默认的php功能?

I know i can use disable_functions directive in php.ini configuration file to disable some default PHP function (for example fopen(), rename, ftp_chdir()……..) in whole website.

disable_functions
disable_functions =”function a, function b, …………. function (n)”

There is a question, if i want some function can run in a.php but cannot run in b.php and c.php , that mean i want to block the function just in some specific page, how can i do it?