diff --git a/core/Api/User/Invite.class.php b/core/Api/User/Invite.class.php
index 9a6b463..4bfdb21 100644
--- a/core/Api/User/Invite.class.php
+++ b/core/Api/User/Invite.class.php
@@ -4,6 +4,7 @@ namespace Api\User;
 
 use Api\Parameter\StringType;
 use \Api\Request;
+use Driver\SQL\Condition\Compare;
 
 class Invite extends Request {
 
@@ -22,8 +23,49 @@ class Invite extends Request {
       return false;
     }
 
-    // TODO:
+    $username = $this->getParam('username');
+    $email = $this->getParam('email');
+    if (!$this->userExists($username, $email) || !$this->success) {
+        return false;
+    }
 
+    $token = generateRandomString(36);
+    $valid_until = (new DateTime())->modify("+48 hour");
+    $sql = $this->user->getSQL();
+    $res = $sql->insert("UserInvite", array("name", "email","token","valid_until"))
+        ->addRow($username, $email, $token,$valid_until)
+        ->execute();
+    $this->success = ($res !== FALSE);
+    $this->lastError = $sql->getLastError();
+
+    if($this->success) {
+        $request = new SendEmail($this->user);
+        $this->success = $request->execute(array(
+            "from" => "...", "to" => $email));
+        $this->lastError  = $request->getLastError();
+    }
     return $this->success;
   }
+
+  private function userExists($username, $email) {
+      $sql = $this->user->getSQL();
+      $res = $sql->select("User.name", "User.email")
+          ->from("User")
+          ->where(new Compare("User.name", $username), new Compare("User.email", $email))
+          ->execute();
+
+      $this->success = ($res !== FALSE);
+      $this->lastError = $sql->getLastError();
+
+      if ($this->success && !empty($res)) {
+          $row = $res[0];
+          if (strcasecmp($username, $row['name']) === 0) {
+              return $this->createError("This username is already taken.");
+          } else if (strcasecmp($username, $row['email']) === 0) {
+              return $this->createError("This email address is already in use.");
+          }
+      }
+
+      return $this->success;
+    }
 }
\ No newline at end of file