PHP not redering all scripts in Mac 10.3

Anyone know why some php code will not render in
Mac 10.3? Having been using Mac 10.1 with no problems, the switch to the newer php caused some
of my php code to stop. Are there some changes from
php 4.0.6 (Mac 10.1) to 4.3.4 (Mac 10.3) that I need
to be aware of when writing this code?