docs: fix incorrect code

Author: kenjis

user_guide_src/source/database/results/013.php

@@ -6,7 +6,7 @@ class User
     public $email;
     public $username;
 
-    protected $last_login;
+    protected $lastLogin;
 
     public function lastLogin($format)
     {

user_guide_src/source/database/results/014.php

@@ -7,5 +7,5 @@
 foreach ($rows as $row) {
     echo $row->id;
     echo $row->email;
-    echo $row->last_login('Y-m-d');
+    echo $row->lastLogin('Y-m-d');
 }

user_guide_src/source/database/results/015.php

@@ -6,5 +6,5 @@
 
 if (isset($row)) {
     echo $row->email;               // access attributes
-    echo $row->last_login('Y-m-d'); // access class methods
+    echo $row->lastLogin('Y-m-d'); // access class methods
 }