fedora core 4

Just installed Fedora Core 4 on my laptop.
Cool man!
The interface is so beautiful!
I love GNOME! :D

Do all the ussual things:
rebuild the MySQL RPM version 5.0.18-standard downloaded from the mysql site. Everything went OK.

rebuild the PHP RPM. Found out that the default version for the FC4 is PHP 5, not PHP 4. There three solutions:

1. downgrade to FC3
2. downgrade the PHP to PHP 5
3. use PHP 5 in the PHP 4 compatibility mode

Since I've done a great deal customizing, the 1st option is out of question.

Then I tried the 2nd option. I've downloaded the src RPM PHP 4 for the FC3. When I tried to rebuild it, it responded with some strange error. After a quick googling, I figured out that FC4 is shipped with GCC 4. GCC 4 is bad! (well, at least for compiling the PHP 4 package for the FC3)

So I take the third option. Edit /etc/php.ini, set parameter: zend.ze1_compatibility_mode to On from it's Off default.
Then run a test....
Extracted a newest jpgraph, the latest pro version 1.21p, which specifically designed for PHP 4, then run the test suit.
Some oops, about some missing True Type fonts.
Do another googling then download the msttcorefont package, to correct this oops.
After this fonts things, the jpgraph test suit seems to load OK.

So can I be sure that the PHP 5 run in compatibility mode will fully compatible with PHP 4??? :-/