These are only notes, it is not finished
CLI - Command-line interface Wikipedia
You need to have installed PHP to be available globally. Type php -v in terminal to check you have it.
Add hash bang on the beginning of the file.
#!php
<?php
echo "Hello" . $argv[1];
Make it executable
chmod +x /path/to/hello.php
And add it to the bin folder, so you can access it from everywhere.
Make a link so changes to the original will be reflected to the global file.
ln -s /path/to/hello.php /usr/local/bin/hello
... or copy the file
cp /path/to/hello.php /usr/local/bin/hello
Run hello ", how are you?" and you will get output Hello, how are you.