find . -type f -name '*.php' -print |
  while read filename
  do
    (
    sed 's/\/home\/tenthumb\/public_html\/public_html\/tenthumbs\/html\//\/home\/tenthumb\/public_html\/html\//i;' $filename >$filename.xxxxx
    mv $filename.xxxxx $filename # replace output files with original
    )
done