diff --git a/Michelf/Markdown.php b/Michelf/Markdown.php
index 746a2d0..f75e476 100644
--- a/Michelf/Markdown.php
+++ b/Michelf/Markdown.php
@@ -5,7 +5,7 @@
  * @package   php-markdown
  * @author    Michel Fortin <michel.fortin@michelf.com>
  * @copyright 2004-2022 Michel Fortin <https://michelf.com/projects/php-markdown/>
- * @copyright (Original Markdown) 2004-2006 John Gruber <https://daringfireball.net/projects/markdown/>
+ * @copyright Original Markdown 2004-2006 John Gruber <https://daringfireball.net/projects/markdown/>
  */
 
 namespace Michelf;
@@ -1079,7 +1079,7 @@ protected function _doLists_callback($matches) {
 			}
 		}
 
-		if ($ol_start > 1 && $list_type == 'ol'){
+		if ($ol_start > 1){
 			$result = $this->hashBlock("<$list_type start=\"$ol_start\">\n" . $result . "</$list_type>");
 		} else {
 			$result = $this->hashBlock("<$list_type>\n" . $result . "</$list_type>");
@@ -1782,7 +1782,7 @@ protected function handleSpanToken($token, &$str) {
 				return $this->hashPart("&#". ord($token[1]). ";");
 			case "`":
 				// Search for end marker in remaining text.
-				if (preg_match('/^(.*?[^`])'.preg_quote($token).'(?!`)(.*)$/sm',
+				if (preg_match('/^(.*?[^`])'.preg_quote($token, '/').'(?!`)(.*)$/sm',
 					$str, $matches))
 				{
 					$str = $matches[2];
diff --git a/Michelf/MarkdownExtra.php b/Michelf/MarkdownExtra.php
index 78e265d..340fdf1 100644
--- a/Michelf/MarkdownExtra.php
+++ b/Michelf/MarkdownExtra.php
@@ -5,7 +5,7 @@
  * @package   php-markdown
  * @author    Michel Fortin <michel.fortin@michelf.com>
  * @copyright 2004-2022 Michel Fortin <https://michelf.com/projects/php-markdown/>
- * @copyright (Original Markdown) 2004-2006 John Gruber <https://daringfireball.net/projects/markdown/>
+ * @copyright Original Markdown 2004-2006 John Gruber <https://daringfireball.net/projects/markdown/>
  */
 
 namespace Michelf;
@@ -218,7 +218,7 @@ protected function teardown() {
 	 * which will be used to populate the id attribute in case it was not
 	 * overridden.
 	 * @param  string $tag_name
-	 * @param  string $attr
+	 * @param  string|null $attr
 	 * @param  mixed  $defaultIdValue
 	 * @param  array  $classes
 	 * @return string
@@ -1796,7 +1796,7 @@ protected function _appendFootnotes_callback($matches) {
 	protected function parseFootnotePlaceholders($label, $footnote_number, $reference_number) {
 		return str_replace(
 			array('^^', '%%'),
-			array($footnote_number, $reference_number),
+			array((string) $footnote_number, (string) $reference_number),
 			$label
 		);
 	}
diff --git a/Michelf/MarkdownInterface.php b/Michelf/MarkdownInterface.php
index 84e6545..ede9155 100644
--- a/Michelf/MarkdownInterface.php
+++ b/Michelf/MarkdownInterface.php
@@ -5,7 +5,7 @@
  * @package   php-markdown
  * @author    Michel Fortin <michel.fortin@michelf.com>
  * @copyright 2004-2022 Michel Fortin <https://michelf.com/projects/php-markdown/>
- * @copyright (Original Markdown) 2004-2006 John Gruber <https://daringfireball.net/projects/markdown/>
+ * @copyright Original Markdown 2004-2006 John Gruber <https://daringfireball.net/projects/markdown/>
  */
 
 namespace Michelf;