AsymetrticKey: add getComment() method

phpseclib/Crypt/Common/AsymmetricKey.php

@@ -115,6 +115,14 @@ abstract class AsymmetricKey
      */
     protected static $engines = [];
 
+    /**
+     * Key Comment
+     *
+     * @var null|string
+     * @access private
+     */
+    private $comment;
+
     /**
      * The constructor
      */
@@ -173,8 +181,10 @@ abstract class AsymmetricKey
         }
 
         $components['format'] = $format;
+        $comment = isset($components['comment']) ? $components['comment'] : null;
         $new = static::onLoad($components);
         $new->format = $format;
+        $new->comment = $comment;
         return $new instanceof PrivateKey ?
             $new->withPassword($password) :
             $new;
@@ -425,6 +435,19 @@ abstract class AsymmetricKey
         return $meta->getShortName();
     }
 
+    /**
+     * Returns the key's comment
+     *
+     * Not all key formats support comments. If you want to set a comment use toString()
+     *
+     * @access public
+     * @return null|string
+     */
+    public function getComment()
+    {
+        return $this->comment;
+    }
+
     /**
      * Tests engine validity
      *