You shouldn't use regex for html parsing of course, but this should separate out
content should you want to. I have limited knowledge of php so this just illustrates procedure.
$tags = 
'  <
   (?:
       /?\w+\s*/?
     | \w+\s+ (?:".*?"|\'.*?\'|[^>]*?)+\s*/?
     | !(?:DOCTYPE.*?|--.*?--)
   )>
';
$scripts =
'   <
   (?:
       (?:script|style) \s*
     | (?:script|style) \s+ (?:".*?"|\'.*?\'|[^>]*?)+\s*
   )>
   .*?
   </(?:script|style)\s*>
';
$regex = / ($scripts | $tags) | ((?:(?!$tags).)+) /xsg;
The replacement string is Group1 catted to the return value of your
word wrap function (which is passed the content, Group2 string)
so something like:  replacement = \1 . textwrap( \2 )
Inside of textwrap you decide what to do with the content.
Tested in Perl (btw its very slow and watered down for clarity):
use strict;
use warnings;
my $tags = 
'  <
   (?:
       /?\w+\s*/?
     | \w+\s+ (?:".*?"|\'.*?\'|[^>]*?)+\s*/?
     | !(?:DOCTYPE.*?|--.*?--)
   )>
';
my $scripts =
'   <
   (?:
       (?:script|style) \s*
     | (?:script|style) \s+ (?:".*?"|\'.*?\'|[^>]*?)+\s*
   )>
   .*?
   </(?:script|style)\s*>
';
my $html = join '', <DATA>;
while ( $html =~ / ($scripts | $tags) | ((?:(?!$tags).)+) /xsg ) {
    if (defined $2 && $2 !~ /^\s+$/) {
        print $2,"\n";
    }
}