I found out the issue is due to an as-yet-undetermined-by-me setting in PHP. To get X-Cart to fully install properly without quitting during the install procedure, I had to modify install.php
Search for any instance where 'init.php' is included in a function. add the following code somewhere within that same function (I usually add it either right over the 'include' statement, or after the opening brace of the function):
Code:
global $HTTP_SERVER_VARS,$HTTP_GET_VARS,$HTTP_COOKIE_VARS,$HTTP_POST_VARS, $HTTP_POST_FILES;
global $reject,$__name,$__avar,$GLOBALS,$HTTP_ENV_VARS;
What happens is prepare.php is called by init.php, and depends upon several variables in PHP being available for parsing. Those variables are not automatically registered as globals within a function (on my PHP install), so that results in prepare.php failing, killing the install script.