diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 80bbeed..ea564de 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -10,12 +10,13 @@ jobs:
     strategy:
       matrix:
         php:
+          - 8.3
+          - 8.2
+          - 8.1
+          - 8.0
           - 7.4
           - 7
           - 5.6
-          - 5.5
-          - 5.4
-          - 5.3
         os: [ubuntu-latest, ubuntu-22.04]
     steps:
       - name: Checkout
diff --git a/Text/Diff/Engine/native.php b/Text/Diff/Engine/native.php
index 25f7ebf..d41eb96 100644
--- a/Text/Diff/Engine/native.php
+++ b/Text/Diff/Engine/native.php
@@ -6,9 +6,9 @@
  *
  * The algorithm used here is mostly lifted from the perl module
  * Algorithm::Diff (version 1.06) by Ned Konz, which is available at:
- * http://www.perl.com/CPAN/authors/id/N/NE/NEDKONZ/Algorithm-Diff-1.06.zip
+ * https://cpan.metacpan.org/authors/id/N/NE/NEDKONZ/Algorithm-Diff-1.06.zip
  *
- * More ideas are taken from: http://www.ics.uci.edu/~eppstein/161/960229.html
+ * More ideas are taken from: https://www.ics.uci.edu/~eppstein/161/960229.html
  *
  * Some ideas (and a bit of code) are taken from analyze.c, of GNU
  * diffutils-2.7, which can be found at:
@@ -20,15 +20,26 @@
  *
  * $Horde: framework/Text_Diff/Diff/Engine/native.php,v 1.7.2.5 2009/01/06 15:23:41 jan Exp $
  *
- * Copyright 2004-2009 The Horde Project (http://www.horde.org/)
+ * Copyright 2004-2009 The Horde Project (https://www.horde.org/)
  *
  * See the enclosed file COPYING for license information (LGPL). If you did
- * not receive this file, see http://opensource.org/licenses/lgpl-license.php.
+ * not receive this file, see https://opensource.org/license/lgpl-3-0/ .
  *
  * @author  Geoffrey T. Dairiki <dairiki@dairiki.org>
  * @package Text_Diff
  */
-class Text_Diff_Engine_native {
+class Text_Diff_Engine_native
+{
+
+    public $xchanged;
+    public $ychanged;
+    public $xv;
+    public $yv;
+    public $xind;
+    public $yind;
+    public $seq;
+    public $in_seq;
+    public $lcs;
 
     function diff($from_lines, $to_lines)
     {
@@ -63,9 +74,11 @@ function diff($from_lines, $to_lines)
         }
 
         // Ignore lines which do not exist in both files.
+        $xhash = [];
         for ($xi = $skip; $xi < $n_from - $endskip; $xi++) {
             $xhash[$from_lines[$xi]] = 1;
         }
+        $yhash = [];
         for ($yi = $skip; $yi < $n_to - $endskip; $yi++) {
             $line = $to_lines[$yi];
             if (($this->ychanged[$yi] = empty($xhash[$line]))) {
@@ -148,7 +161,7 @@ function diff($from_lines, $to_lines)
      * match.  The caller must trim matching lines from the beginning and end
      * of the portions it is going to specify.
      */
-    function _diag ($xoff, $xlim, $yoff, $ylim, $nchunks)
+    function _diag($xoff, $xlim, $yoff, $ylim, $nchunks)
     {
         $flip = false;
 
@@ -160,6 +173,7 @@ function _diag ($xoff, $xlim, $yoff, $ylim, $nchunks)
                 = array($yoff, $ylim, $xoff, $xlim);
         }
 
+        $ymatches = array();
         if ($flip) {
             for ($i = $ylim - 1; $i >= $yoff; $i--) {
                 $ymatches[$this->xv[$i]][] = $i;
@@ -173,7 +187,7 @@ function _diag ($xoff, $xlim, $yoff, $ylim, $nchunks)
         $this->lcs = 0;
         $this->seq[0]= $yoff - 1;
         $this->in_seq = array();
-        $ymids[0] = array();
+        $ymids = array(array());
 
         $numer = $xlim - $xoff + $nchunks - 1;
         $x = $xoff;
@@ -192,15 +206,16 @@ function _diag ($xoff, $xlim, $yoff, $ylim, $nchunks)
                 }
                 $matches = $ymatches[$line];
                 reset($matches);
-                foreach ($matches as list(, $y)) {
+                while ($y = current($matches)) {
                     if (empty($this->in_seq[$y])) {
                         $k = $this->_lcsPos($y);
                         assert($k > 0);
                         $ymids[$k] = $ymids[$k - 1];
                         break;
                     }
+                    next($matches);
                 }
-                foreach ($matches as list(, $y)) {
+                while ($y = current($matches)) {
                     if ($y > $this->seq[$k - 1]) {
                         assert($y <= $this->seq[$k]);
                         /* Optimization: this is a common case: next match is
@@ -213,11 +228,12 @@ function _diag ($xoff, $xlim, $yoff, $ylim, $nchunks)
                         assert($k > 0);
                         $ymids[$k] = $ymids[$k - 1];
                     }
+                    next($matches);
                 }
             }
         }
 
-        $seps[] = $flip ? array($yoff, $xoff) : array($xoff, $yoff);
+        $seps = array($flip ? array($yoff, $xoff) : array($xoff, $yoff));
         $ymid = $ymids[$this->lcs];
         for ($n = 0; $n < $nchunks - 1; $n++) {
             $x1 = $xoff + (int)(($numer + ($xlim - $xoff) * $n) / $nchunks);
@@ -268,7 +284,7 @@ function _lcsPos($ypos)
      * Note that XLIM, YLIM are exclusive bounds.  All line numbers are
      * origin-0 and discarded lines are not counted.
      */
-    function _compareseq ($xoff, $xlim, $yoff, $ylim)
+    function _compareseq($xoff, $xlim, $yoff, $ylim)
     {
         /* Slide down the bottom initial diagonal. */
         while ($xoff < $xlim && $yoff < $ylim
@@ -309,7 +325,7 @@ function _compareseq ($xoff, $xlim, $yoff, $ylim)
             reset($seps);
             $pt1 = $seps[0];
             while ($pt2 = next($seps)) {
-                $this->_compareseq ($pt1[0], $pt2[0], $pt1[1], $pt2[1]);
+                $this->_compareseq($pt1[0], $pt2[0], $pt1[1], $pt2[1]);
                 $pt1 = $pt2;
             }
         }