Follow these instructions to get the ads showing on PHP based websites. You will need FTP access and the ability to change file permissions on your server. It would be handy if you have a template or fheader/footer file in which you can display the ads. Otherwise you will have to copy and paste it into all pages within the Base URL tree.
To change the ad type from banner to text or text to image banner etc. see here in Part 1.
As of early April you can now have all the formatting done for you in the Setup Instructions part of your account. It now features a drop-down to select the number of ads to be displayed (1 to 5) and it has a form element to choose your favourite method of separation. It defaults to which will vertially align the ads. Other popular options are , , , and other characters. Note the single space before and after the | and / etc. All ads are now displayed by a single "echo $ad_network;" line. Some people prepend this with a line of text like this:
Sorry for the line formatting - Blogger is a nightmare in that regard!
Don't forget to follow the rest of the official instructions - especially setting the .txt file as being writable!