when you are using linux/unix that will suffice
#!/usr/bin/php
if that isnt working, try
which php
a non-empty output shows you, that there is a php installed,
try to correct the shebang-line
if you are using windows:
there is no shebang-line, you'll need to specify how to use that script
try php <SCRIPTNAME> on the command-line
if thats not working, try php --version
if there is an error in the output, you'll need to add the php to the path( where php.exe is located )