RewriteMap lc int:tolower

RewriteEngine On
RewriteBase /
RewriteCond %{REQUEST_URI} ^[^A-Z]*[A-Z].*
RewriteRule ^ ${lc:%{REQUEST_URI}} [L,R=301]

RewriteEngine On
RewriteBase /
RewriteCond %{REQUEST_URI} [A-Z]
RewriteRule (.*) ${lc:$1} [R=301,L]

RewriteEngine On
RewriteBase /

# If there are caps, set HASCAPS to true and skip next rule
RewriteRule [A-Z] - [E=HASCAPS:TRUE,S=1]

# Skip this entire section if no uppercase letters in requested URL
RewriteRule ![A-Z] - [S=28]

# Replace single occurance of CAP with cap, then process next Rule.
RewriteRule ^([^A]*)A(.*)$ $1a$2
RewriteRule ^([^B]*)B(.*)$ $1b$2
RewriteRule ^([^C]*)C(.*)$ $1c$2
RewriteRule ^([^D]*)D(.*)$ $1d$2
RewriteRule ^([^E]*)E(.*)$ $1e$2
RewriteRule ^([^F]*)F(.*)$ $1f$2
RewriteRule ^([^G]*)G(.*)$ $1g$2
RewriteRule ^([^H]*)H(.*)$ $1h$2
RewriteRule ^([^I]*)I(.*)$ $1i$2
RewriteRule ^([^J]*)J(.*)$ $1j$2
RewriteRule ^([^K]*)K(.*)$ $1k$2
RewriteRule ^([^L]*)L(.*)$ $1l$2
RewriteRule ^([^M]*)M(.*)$ $1m$2
RewriteRule ^([^N]*)N(.*)$ $1n$2
RewriteRule ^([^O]*)O(.*)$ $1o$2
RewriteRule ^([^P]*)P(.*)$ $1p$2
RewriteRule ^([^Q]*)Q(.*)$ $1q$2
RewriteRule ^([^R]*)R(.*)$ $1r$2
RewriteRule ^([^S]*)S(.*)$ $1s$2
RewriteRule ^([^T]*)T(.*)$ $1t$2
RewriteRule ^([^U]*)U(.*)$ $1u$2
RewriteRule ^([^V]*)V(.*)$ $1v$2
RewriteRule ^([^W]*)W(.*)$ $1w$2
RewriteRule ^([^X]*)X(.*)$ $1x$2
RewriteRule ^([^Y]*)Y(.*)$ $1y$2
RewriteRule ^([^Z]*)Z(.*)$ $1z$2

# If there are any uppercase letters, restart at very first RewriteRule in file.
RewriteRule [A-Z] - [N]

RewriteCond %{ENV:HASCAPS} TRUE
RewriteRule ^/?(.*) /$1 [R=301,L]

if ( $_SERVER['REQUEST_URI'] != strtolower( $_SERVER['REQUEST_URI']) ) {
    header('Location: http://'.$_SERVER['HTTP_HOST'] .
            strtolower($_SERVER['REQUEST_URI']), true, 301);
    exit();
}