diff --git a/api/user.php b/api/user.php
index 84934ee..7b88d0c 100644
--- a/api/user.php
+++ b/api/user.php
@@ -33,6 +33,13 @@ if(DB :: isError($conn)) {
 }
 $conn->setFetchMode(DB_FETCHMODE_ORDERED);
 
+/* Valid API KEY (defined in credentials.php) ? */
+if(!isset($_GET['apikey']) || $_GET['apikey'] !== USER_API_KEY) {
+    set_response_code(400);
+    echo json_encode(array('error' => "Invalid apikey."));
+    die();
+}
+
 /* Validate params */
 if(!isset($_GET['q'])) {
     set_response_code(400);
diff --git a/inside/credentials-sample.php b/inside/credentials-sample.php
index 2d616f7..87fcb5c 100644
--- a/inside/credentials-sample.php
+++ b/inside/credentials-sample.php
@@ -24,4 +24,7 @@ function getDSN($host = "default") {
 
 	return "$driver://$user_name:$password@$host_name/$db_name";
 }
+
+define("USER_API_KEY", "");
+
 ?>