Gotcha Of The Day - Relative Paths In Apache Rewrite Rules

I launched one of my client's sites last night, and wanted to make the old pages automatically redirect to the new ones.

I could have written a manual series of Apache Rewrite Rules to this, but the majority of the page names stayed the same, so I was hoping I could get a bit fancier than that. I worked up the following rule:

RewriteCond %{REQUEST_URI}              ^/(.*)
RewriteCond newdir/%1 -f
RewriteRule ^(.*) http://www.clientsite.com/newdir/$1 [R=301,L]

Which does the follow:

• Grabs everything after the slash in the request URI and stores it in %1 (/foo.php stores foo.php in %1)
• Checks for the existing of the file in newdir (does newdir/foo.php exist?)
• If so, then redirect to that URL

Alas, this wasn't working. I figured out that the -f check was failing. The fix? To not assume the relative path newdir/foo.php would be found. Instead, use the %{DOCUMENT_ROOT} variable to build up and compare an absolute path.

RewriteCond %{REQUEST_URI}              ^/(.*)
RewriteCond %{DOCUMENT_ROOT}/newdir/%1 -f
RewriteRule ^(.*)  http://www.customersite.com/newdir/$1 [R=301,L]

Man I love Apache Rewrite Rules - they can be cryptic, but well worth getting to to know and master.