make it so BigIntegers can be JSON serialized

phpseclib/Math/BigInteger.php

@@ -40,7 +40,7 @@ use phpseclib3\Math\BigInteger\Engines\Engine;
  * @author  Jim Wigginton <terrafrost@php.net>
  * @access  public
  */
-class BigInteger
+class BigInteger implements \JsonSerializable
 {
     /**
      * Main Engine
@@ -438,6 +438,20 @@ class BigInteger
         }
     }
 
+    /**
+     * JSON Serialize
+     *
+     * Will be called, automatically, when json_encode() is called on a BigInteger object.
+     */
+    public function jsonSerialize()
+    {
+        $result = ['hex' => $this->toHex(true)];
+        if ($this->precision > 0) {
+            $result['precision'] = $this->getPrecision();
+        }
+        return $result;
+    }
+
     /**
      * Performs modular exponentiation.
      *

phpseclib/Math/BigInteger/Engines/Engine.php

@@ -28,7 +28,7 @@ use phpseclib3\Math\BigInteger;
  * @author  Jim Wigginton <terrafrost@php.net>
  * @access  public
  */
-abstract class Engine
+abstract class Engine implements \JsonSerializable
 {
     /* final protected */ const PRIMES = [
         3,   5,   7,   11,  13,  17,  19,  23,  29,  31,  37,  41,  43,  47,  53,  59,
@@ -371,6 +371,20 @@ abstract class Engine
         }
     }
 
+    /**
+     * JSON Serialize
+     *
+     * Will be called, automatically, when json_encode() is called on a BigInteger object.
+     */
+    public function jsonSerialize()
+    {
+        $result = ['hex' => $this->toHex(true)];
+        if ($this->precision > 0) {
+            $result['precision'] = $this->precision;
+        }
+        return $result;
+    }
+
     /**
      * Converts a BigInteger to a base-10 number.
      *

phpseclib/Math/Common/FiniteField/Integer.php

@@ -21,6 +21,18 @@ namespace phpseclib3\Math\Common\FiniteField;
  * @author  Jim Wigginton <terrafrost@php.net>
  * @access  public
  */
-abstract class Integer
+abstract class Integer implements \JsonSerializable
 {
+    /**
+     * JSON Serialize
+     *
+     * Will be called, automatically, when json_encode() is called on a BigInteger object.
+     *
+     * PHP Serialize isn't supported because unserializing would require the factory be
+     * serialized as well and that just sounds like too much
+     */
+    public function jsonSerialize()
+    {
+        return ['hex' => $this->toHex(true)];
+    }
 }