diff --git a/src/BarcodeGeneratorDynamicHTML.php b/src/BarcodeGeneratorDynamicHTML.php
index d2e7cb5..52809d3 100644
--- a/src/BarcodeGeneratorDynamicHTML.php
+++ b/src/BarcodeGeneratorDynamicHTML.php
@@ -11,11 +11,11 @@ class BarcodeGeneratorDynamicHTML extends BarcodeGenerator
      * This 'dynamic' version uses percentage based widths and heights, resulting in a vector-y qualitative result.
      *
      * @param string $barcode code to print
-     * @param string $type type of barcode
+     * @param BarcodeGenerator::Type_* $type (string) type of barcode
      * @param string $foregroundColor Foreground color for bar elements as '#333' or 'orange' for example (background is transparent).
      * @return string HTML code.
      */
-    public function getBarcode($barcode, $type, string $foregroundColor = 'black')
+    public function getBarcode(string $barcode, $type, string $foregroundColor = 'black'): string
     {
         $barcodeData = $this->getBarcodeData($barcode, $type);
 
diff --git a/src/BarcodeGeneratorHTML.php b/src/BarcodeGeneratorHTML.php
index 25a8820..294b680 100644
--- a/src/BarcodeGeneratorHTML.php
+++ b/src/BarcodeGeneratorHTML.php
@@ -9,13 +9,13 @@ class BarcodeGeneratorHTML extends BarcodeGenerator
      * This original version uses pixel based widths and heights. Use Dynamic HTML version for better quality representation.
      *
      * @param string $barcode code to print
-     * @param string $type type of barcode
+     * @param BarcodeGenerator::Type_* $type (string) type of barcode
      * @param int $widthFactor Width of a single bar element in pixels.
      * @param int $height Height of a single bar element in pixels.
      * @param string $foregroundColor Foreground color for bar elements as '#333' or 'orange' for example (background is transparent).
      * @return string HTML code.
      */
-    public function getBarcode($barcode, $type, int $widthFactor = 2, int $height = 30, string $foregroundColor = 'black')
+    public function getBarcode($barcode, $type, int $widthFactor = 2, int $height = 30, string $foregroundColor = 'black'): string
     {
         $barcodeData = $this->getBarcodeData($barcode, $type);
 
diff --git a/src/BarcodeGeneratorPNG.php b/src/BarcodeGeneratorPNG.php
index e73a054..bc7943c 100644
--- a/src/BarcodeGeneratorPNG.php
+++ b/src/BarcodeGeneratorPNG.php
@@ -11,6 +11,9 @@ class BarcodeGeneratorPNG extends BarcodeGenerator
 {
     protected $useImagick = true;
 
+    /**
+     * @throws BarcodeException
+     */
     public function __construct()
     {
         // Auto switch between GD and Imagick based on what is installed
@@ -43,13 +46,13 @@ public function useGd()
      * Return a PNG image representation of barcode (requires GD or Imagick library).
      *
      * @param string $barcode code to print
-     * @param string $type type of barcode:
+     * @param BarcodeGenerator::Type_* $type (string) type of barcode
      * @param int $widthFactor Width of a single bar element in pixels.
      * @param int $height Height of a single bar element in pixels.
      * @param array $foregroundColor RGB (0-255) foreground color for bar elements (background is transparent).
      * @return string image data or false in case of error.
      */
-    public function getBarcode($barcode, $type, int $widthFactor = 2, int $height = 30, array $foregroundColor = [0, 0, 0])
+    public function getBarcode(string $barcode, $type, int $widthFactor = 2, int $height = 30, array $foregroundColor = [0, 0, 0]): string
     {
         $barcodeData = $this->getBarcodeData($barcode, $type);
         $width = round($barcodeData->getWidth() * $widthFactor);
diff --git a/src/BarcodeGeneratorSVG.php b/src/BarcodeGeneratorSVG.php
index 6f8fb16..e67527f 100644
--- a/src/BarcodeGeneratorSVG.php
+++ b/src/BarcodeGeneratorSVG.php
@@ -15,7 +15,7 @@ class BarcodeGeneratorSVG extends BarcodeGenerator
      * @return string SVG code.
      * @public
      */
-    public function getBarcode(string $barcode, $type, float $widthFactor = 2, float $height = 30, string $foregroundColor = 'black')
+    public function getBarcode(string $barcode, $type, float $widthFactor = 2, float $height = 30, string $foregroundColor = 'black'): string
     {
         $barcodeData = $this->getBarcodeData($barcode, $type);