Migration from PHP 3.0 to PHP 4.0 is relatively easy, and should not require you to change your code in any way. There are minor incompatibilities between the two versions; You may want to check the incompatibilities list to make sure that you're indeed not affected by them (the chances you're affected by these incompatibilities are extremely slim).

Running PHP 3.0 and PHP 4.0 concurrently

Many of you are probably interested to know whether it's possible to run both PHP 3.0 and PHP 4.0 in the same server, for the duration of the transition period. Well, the simple answer is that you can't. PHP 3.0 and PHP 4.0 share a lot of common code (not in the language itself, but in the module code) and for many technical reasons, compiling the two versions into the same server is not possible. We don't expect this to change in future betas or the final release.

However, this shouldn't have too much impact on you, for two reasons:

The close to 100% compatibility PHP 4.0 features mean that most chances are that your web site would run with PHP 4.0 without requiring any additional work on your side. Note that PHP 4.0 Beta 1 is, as its name implies, still a beta, so there'll probably be bugs - don't try PHP 4.0 Beta 1 on your production web site before testing it offline on a different machine or port!
If you're still not sure, and want to slowly migrate from PHP 3.0 to PHP 4.0 - you can run PHP 4.0 as a server module, and PHP 3.0 as a CGI binary (or vice versa).

Migrating Configuration Files

Global Configuration File

The global configuration file, php3.ini, has changed its name to php.ini.

Apache Configuration Files

The MIME types recognized by the PHP module have changed:

application/x-httpd-php3 --> application/x-httpd-php

application/x-httpd-php3-source --> application/x-httpd-php-source

You can make your configuration files work with both versions of PHP (depending on which one is currently compiled into the server), using the following syntax:


AddType .php3 application/x-httpd-php3
AddType .phps application/x-httpd-php3-source


AddType .php3 application/x-httpd-php
AddType .phps application/x-httpd-php-source

In addition, the PHP directive names for Apache have changed.

Starting with PHP 4.0, there are only four Apache directives that relate to PHP:

php_value [PHP directive name] [value]

php_flag [PHP directive name] [On|Off]

php_admin_value [PHP directive name] [value]

php_admin_flag [PHP directive name] [On|Off]

There are two differences between the Admin values and the non admin values:

Admin values (or flags) can only appear in the Server-wide apache configuration files (e.g., httpd.conf).
Standard values (or flags) cannot control certain PHP directives, for example - safe mode (if you could override safe mode settings in .htaccess files, it would defeat safe-mode's purpose). In contrast, Admin values can modify the value of any PHP directive.

To make the transition process easier, PHP 4.0 is bundled with scripts that automatically convert your Apache configuration and .htaccess files to work with both PHP 3.0 and PHP 4.0. These scripts do NOT convert the mime type lines! You have to convert these yourself.

To convert your Apache configuration files, run the apconf-conv.sh script (available in the scripts/apache/ directory). For example:

~/php4/scripts/apache:# ./apconf-conv.sh /usr/local/apache/conf/httpd.conf

Your original configuration file will be saved in httpd.conf.orig.

To convert your .htaccess files, run the aphtaccess-conv.sh script (available in the scripts/apache/ directory as well):

~/php4/scripts/apache:# find / -name .htaccess -exec ./aphtaccess-conv.sh {} \;

Likewise, your old .htaccess files will be saved with an .orig prefix.

The conversion scripts require awk to be installed.