CrobJob on Task Menu

Hello

I try to create new crobjob by Tools->task

and i create Task first to task tab.. but on command textbox i put <folder>/php file but its always said
/bin/sh:1: <folder>/php file: not found and i try like below too
/bin/sh:1: /<main folder>/<folder>/php file: permission denied

second try said permission denied. What happen? folder that i create from Website Menu

Thank You