diff --git a/.github/FUNDING.yml b/.github/FUNDING.yml
new file mode 100644
index 0000000..ca5b429
--- /dev/null
+++ b/.github/FUNDING.yml
@@ -0,0 +1 @@
+custom: ['https://www.paypal.com/cgi-bin/webscr?cmd=_donations&currency_code=GBP&business=paypal@tecnick.com&item_name=donation%20for%20tcpdf%20project']
diff --git a/include/barcodes/datamatrix.php b/include/barcodes/datamatrix.php
index 19b46fa..783f99d 100644
--- a/include/barcodes/datamatrix.php
+++ b/include/barcodes/datamatrix.php
@@ -629,7 +629,7 @@ class Datamatrix {
 					if ($numch[ENC_C40] == $numch[ENC_X12]) {
 						$k = ($pos + $charscount + 1);
 						while ($k < $data_length) {
-							$tmpchr = ord($data{$k});
+							$tmpchr = ord($data[$k]);
 							if ($this->isCharMode($tmpchr, ENC_X12)) {
 								return ENC_X12;
 							} elseif (!($this->isCharMode($tmpchr, ENC_X12) OR $this->isCharMode($tmpchr, ENC_C40))) {
diff --git a/tcpdf.php b/tcpdf.php
index 4dedf41..ab5e138 100644
--- a/tcpdf.php
+++ b/tcpdf.php
@@ -4722,7 +4722,7 @@ class TCPDF {
 	 */
 	public function SetLink($link, $y=0, $page=-1) {
 		$fixed = false;
-		if (!empty($page) AND is_string($page) AND ($page[0] == '*')) {
+		if (!empty($page) AND (substr($page, 0, 1) == '*')) {
 			$page = intval(substr($page, 1));
 			// this page number will not be changed when moving/add/deleting pages
 			$fixed = true;
@@ -12279,7 +12279,7 @@ class TCPDF {
 			$x = $this->w;
 		}
 		$fixed = false;
-		if (!empty($page) AND ($page[0] == '*')) {
+		if (!empty($page) AND (substr($page, 0, 1) == '*')) {
 			$page = intval(substr($page, 1));
 			// this page number will not be changed when moving/add/deleting pages
 			$fixed = true;
@@ -12382,7 +12382,7 @@ class TCPDF {
 			$x = $this->w;
 		}
 		$fixed = false;
-		if (!empty($page) AND ($page[0] == '*')) {
+		if ((string)$page && (((string)$page)[0] == '*')) {
 			$page = intval(substr($page, 1));
 			// this page number will not be changed when moving/add/deleting pages
 			$fixed = true;