PHP3 to PHP4

[Anon]

I am working with hosts that still only have PHP3 on their servers. I want to use PHP4 and was wondering if it is backwards compatible with PHP3.

[dcomartin]

I was in the same sort of situation John. Our server was running PHP3, but I was developing under PHP4. There are some minor differences between the two.

Firstly, anytime you call a built-in PHP function, take a quick look in the manual to see if it's availible in PHP3. Also global GPC variables are always on in PHP3, they can be turned off in PHP4. So it's good practice to the $HTTP*VARS array for GPC variables. You can turn this on in your php3.ini file, and its always on as of PHP 4.0.3

Also, some $HTTP_SERVER_VARS elements do not exists, so keep an eye out for them. I can't remember which ones exacly. Hope this helps.

Derek C