Compare 2 html files and display difference

I am using a script HtmlDiff.php to compare 2 files and display and highlight differences.
Now I want the % (percentage) of difference between them. I am attaching the HtmlDiff.php here.
I tried to use similar_text , but it hangs there because of the large text.

 

can't you do something like the following

<?php
$count1= mb_strlen( $text1 );
$count2= mb_strlen( $text2 );
 
if ($text1 >= $text2){
   $count[0]['text']     = $text1;
   $count[1]['text']     = $text2;
   }else{
       $count[0]['text']     = $text2;
       $count[1]['text']     = $text1;
       }
 
$percent = ($count[0]['text'] / $count[1]['text']) * 100;
?>

Code (markup):

 

Not sure if this will be any better than similar_text(), but it's easy to do. Though not as accurate (well, different).

function percentage($string, $string2){
   $percent = levenshtein($string, $string2);
   $l = strlen($string);
   $l2 = strlen($string2);
   
   $l = ($l2 >= $l) ? $l2 : $l; 
   
   return (1 - ($percent/$l))*100 . '%';
}

PHP:

Takes the difference in characters between the two strings using levenshtein, then divides it by the length of the longest string, so the results will be different to similar text but makes sense mathematically. I think.