This story was covered recently at planet-php.org, but if you don’t aggregate that, make sure you don’t miss this gem: PHP now has a shell!
I remember this being promised and blogged about around a year ago, but it doesn’t seem to have materialized until now. If you’ve used the Python interactive shell, you immediately notice how PHP’s equivalent is the poor relation.
For the last few years I’ve been trying to build the considerable patience required to use the default shell available in PHP. If you have any parse errors, it dies, and of course you have to keep typing "<?php" everytime you re-fire it up.
Jan’s version is a considerable improvement, and although it doesn’t yet handle up-arrow for previous LOC or back-arrow in case you type your parentheses first and want to fill in the variables after, it’s a welcome relief to work with. I’m sure it will delay the capitulation when you give up and create a stupid file and request it in a browser just to test some little PHP detail.