No, changing the first line and the extension should make everything work fine. If you provider has it set up correctly. You may also have to make the file executable. chmod +x <file>
The line that they are asking you to add is a special line in UNIX/Linx it's called a she-bang. It tells the OS that to run the file it needs to use the given parser. So #!/usr/bin/php tells the OS that the file it's looking at is understood by the program called php in the /usr/bin directory so the OS just passes off control of the file to that program.
