1) you might need to use the path to the directory for mysql (or change into that directory) in order to use the command. Does Mac allow you to have global app names that you can just type? i forget the term.
2) php is weird. if you're used to java (like i am) and you do an error in PHP you're going to start ripping your hair out - blank pages means there's an error and your php file isn't configured to show all errors. try adding this to the top of your script:
You can also use mysql_error() and die() to catch errors in your code like this:
mysql_connect($host,$user,$pass) or die('unable to connect to server: '.mysql_error());