Did it work before GD was installed?

Meh, didn't see that this was in installer itself.

bugzilla wrote:

Max, before GD was installed (or any of its prerequisite packages, I reckon), I was indeed getting to the language selection screen (the very first screen after clicking the "Please complete the installation" link on the new deployment), as well as the next screen that reported on the environment - all without any web server errors.

After GD was installed, clicking the "Please complete the installation" link was generating server error 500 as reported above. I've even tried blowing away the mediawiki directory and re-extracting the .tar.gz, to reset the install process - still the same error. So it must be due to the environmental change as a result of GD.

bugzilla wrote:

Here are the exact effects from running sudo yum install php-gd :

[root@corp1]# cat /var/log/yum.log | grep 'Jul 13 '
Jul 13 15:27:58 Updated: php-common-5.3.14-2.21.amzn1.x86_64
Jul 13 15:27:59 Updated: php-cli-5.3.14-2.21.amzn1.x86_64
Jul 13 15:27:59 Updated: php-pdo-5.3.14-2.21.amzn1.x86_64
Jul 13 15:27:59 Installed: libXpm-3.5.8-2.8.amzn1.x86_64
Jul 13 15:27:59 Installed: t1lib-5.1.2-6.5.amzn1.x86_64
Jul 13 15:27:59 Installed: php-gd-5.3.14-2.21.amzn1.x86_64
Jul 13 15:28:00 Updated: php-mysql-5.3.14-2.21.amzn1.x86_64
Jul 13 15:28:00 Updated: php-5.3.14-2.21.amzn1.x86_64

uothrawn wrote:

Issue appears to be in function secureAndSplit inside Title.php, this line is returning NULL:

$dbkey = preg_replace( '/[ _\xA0\x{1680}\x{180E}\x{2000}-\x{200A}\x{2028}\x{2029}\x{202F}\x{205F}\x{3000}]+/u', '_', $dbkey );

Stacktrace needed to see the caller stack and find the Title::newFromText or Title::makeTitleSafe call. Than it can be checked, if the return value of that method is check against null before using.