[Mediawiki-l] help upgrading 1.5.6 to 1.6.3

[Greg Rodenhiser]

I am attempting to upgrade Mediawiki 1.5.6 to the latest (1.6.3).  I have
backed up all files and the MySQL database.  I then copied over the original
1.5.6 directory with the new 1.6.3 directory.  Next, I ran php -cli
./maintenance/update.php and get the following error:

Fatal error: Call to undefined function socket_sendto() in
<MEDIAWIKI>/includes/GlobalFunctions.php on line 1506

I have also tried using the web interface to run the upgrade and the same
error message appears.  I have also tried just upgrading to Mediawiki
1.6.2and the same isue persists.  Below is the versions of applicable
software I
have:

Mediawiki: 1.5.6
PHP 5.0.5 (apache2handler)
MySQL 4.1.15-Max
OS: Redhat Enterprise 3AS

I'd really appreciate it if someone can point out what I'm doing wrong and
recommend how to complete the upgrade.  Thanks in advance!!