A very interesting article posted on the phparch blog explains how MySQL will be debudled from PHP5. SQLive will come as a bundled application.
On Jeremy's blog It came to my attention that
"If you use the PHP-MySQL extension to build an application and you distribute that commercially, you must buy a MySQL license. Or, if you commercially redistribute a PHP binary that is linked with MySQL (which is most often the case if it is bundled), then you need to buy a MySQL license."

Personally, and without having studied the legal mambo behind the MySql hybrid licensing, I am not very optimistic about these high fees. For instance, I found a bit fuzzy for MySQL to ask over 2000 Euro for a 5 days training course ...read more

True every commercial company needs to make money out of it, but I would rather appreciate separate fees for students and corporate clients.

Occasionally, I came across SQLite (during the setup for the unofficial php.net mirror at dotgeek we realized that php.net is not using mysql but only SQLite as a database) and WOAH what a thing.

In many, many and again many cases this is an ideal solution for small and mid-size projects. It could even work on bigger projects, php.net is certainly not a small/low traffic website.

Just yesterday night I finished a new simple script for the new dotgeek news system and ...I had the idea to migrate this small set of scripts from mysql to sqlite.

I found an excellent frontend for SQLite called sqlitemanager which comes very handy.
Then I managed to have my DB connection class changed to sqlite (thanks Eljas) and guess what? all works as advertised. Installation under php 4 is dead easy " pear install SQLite" et voila.

PHP5 will come with SQlite default, and this is a great thing. There is an excellent introductory tutorial and explanation prepared by a PHP code developer just here worth a deep look.

Oh right, in case you wonder " it's two times faster than both mySQL and Postgres on simple operations, implements an impressive amount of the SQL92 standard (including transaction support) and has bindings for Tcl, PHP, Perl, Python and Java. "

moreover "is released under a no-holds-barred public domain license that practically begs you to include it in your applications, commercial or not."

Of course there is a debate going on over the php internals...
Whilst I am far from being a database expert, I do know that SQLite is an ideal solution for small and mid sized projects and, in many cases, is far more flexible then MySql.

The list of self explanatory functions is on the manual .
Cheers
gurugeek