Index: library/Zend/Json.php
===================================================================
--- library/Zend/Json.php       (revision 24415)
+++ library/Zend/Json.php       (working copy)
@@ -125,8 +125,12 @@
      */
     public static function encode($valueToEncode, $cycleCheck = false, $options = array())
     {
-        if (is_object($valueToEncode) && method_exists($valueToEncode, 'toJson')) {
-            return $valueToEncode->toJson();
+        if (is_object($valueToEncode)) {
+            if (method_exists($valueToEncode, 'toJson')) {
+                return $valueToEncode->toJson();
+            } elseif (method_exists($valueToEncode, 'toArray')) {
+                return self::encode($valueToEncode->toArray(), $cycleCheck, $options);
+            }
         }

         // Pre-encoding look for Zend_Json_Expr objects and replacing by tmp ids
Index: tests/Zend/JsonTest.php
===================================================================
--- tests/Zend/JsonTest.php     (revision 24415)
+++ tests/Zend/JsonTest.php     (working copy)
@@ -811,7 +811,28 @@
         $this->assertEquals($targetHtmlOutput, Zend_Json::prettyPrint($jsonstr, array('format' => 'html')));
     }

+    /**
+     * @group ZF-11167
+     */
+    public function testEncodeWillUseToArrayMethodWhenAvailable()
+    {
+        $o = new ZF11167_ToArrayClass();
+        $objJson = Zend_Json::encode($o);
+        $arrJson = Zend_Json::encode($o->toArray());
+        $this->assertSame($arrJson, $objJson);
+    }

+    /**
+     * @group ZF-11167
+     */
+    public function testEncodeWillUseToJsonWhenBothToJsonAndToArrayMethodsAreAvailable()
+    {
+        $o = new ZF11167_ToArrayToJsonClass();
+        $objJson = Zend_Json::encode($o);
+        $this->assertEquals('"bogus"', $objJson);
+        $arrJson = Zend_Json::encode($o->toArray());
+        $this->assertNotSame($objJson, $arrJson);
+    }

 }

@@ -868,6 +889,41 @@
 }

 /**
+ * Serializable class exposing a toArray() method
+ * @see ZF-11167
+ */
+class ZF11167_ToArrayClass
+{
+    private $_firstName = 'John';
+
+    private $_lastName = 'Doe';
+
+    private $_email = 'john@doe.com';
+
+    public function toArray()
+    {
+        $data = array(
+            'firstName' => $this->_firstName,
+            'lastName'  => $this->_lastName,
+            'email'     => $this->_email
+        );
+        return $data;
+    }
+}
+
+/**
+ * Serializable class exposing both toArray() and toJson() methods
+ * @see ZF-11167
+ */
+class ZF11167_ToArrayToJsonClass extends ZF11167_ToArrayClass
+{
+    public function toJson()
+    {
+        return Zend_Json::encode('bogus');
+    }
+}
+
+/**
  * ISSUE  ZF-4946
  *
  */