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-- Sitemaps, Meta Data, and robots.txt
---- Apache: execute "global" php script when robots.txt requested
lucy24 - 7:53 pm on Aug 20, 2012 (gmt 0)Thread source:: http://www.webmasterworld.com/robots_txt/4486406.htm
If you're doing that, don't you have to put a separate "robots.php" file in each domain? I got the impression that's what the OP was trying to avoid.
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