This faq section will help you migrate from PHP 4 to PHP 5.
Although PHP 5 offers many new features, it's designed to be as compatible with earlier versions of PHP as possible with little functionality being broken in the process.
Be sure to read the appropriate PHP 5 migration appendix of this manual as it contains even more information on the topic of migrating to PHP 5.
MySQL is supported with the only
change being that MySQL support is no longer enabled by
default in PHP 5. This essentially means that
PHP doesn't include the
option in the configure line so
that you must now manually do this when compiling PHP. Windows users will
edit php.ini and enable the php_mysql.dll DLL as
in PHP 4 no such DLL existed, it was simply built into your Windows
Also, the MySQL client libraries are no longer bundled with PHP. More
details on this topic are covered in
the following FAQ and
be sure to read the MySQL section
for details on installing MySQL. An example configure line would be
--with-mysql=/usr while Windows users
will need the libmySQL.dll available to the system.
Few other changes exist, see the migration 5 appendix for details. There won't be a PHP 5 specific version of the manual as the bulk of PHP remains the same.