Slim Application Error

The application could not run because of the following error:

Details

Type: ErrorException
Code: 2
Message: Undefined array key "slim.flash"
File: /export/depts/fas/centres/kedb/engage/erdf-projects/header.php
Line: 6

Trace

#0 /export/depts/fas/centres/kedb/engage/erdf-projects/header.php(6): Slim\Slim::handleErrors(2, &
#039;Undefined array...&
#039;, &
#039;/export/depts/f...&
#039;, 6)
#1 /export/depts/fas/centres/kedb/engage/erdf-projects/business_register_form.php(2): require_once(&
#039;/export/depts/f...&
#039;)
#2 /export/depts/fas/centres/kedb/engage/index.php(120): include(&
#039;/export/depts/f...&
#039;)
#3 [internal function]: {closure}()
#4 /export/depts/fas/centres/kedb/engage/Slim/Route.php(468): call_user_func_array(Object(Closure), Array)
#5 /export/depts/fas/centres/kedb/engage/Slim/Slim.php(1357): Slim\Route->dispatch()
#6 /export/depts/fas/centres/kedb/engage/Slim/Middleware/Flash.php(85): Slim\Slim->call()
#7 /export/depts/fas/centres/kedb/engage/Slim/Middleware/MethodOverride.php(92): Slim\Middleware\Flash->call()
#8 /export/depts/fas/centres/kedb/engage/Slim/Middleware/PrettyExceptions.php(67): Slim\Middleware\MethodOverride->call()
#9 /export/depts/fas/centres/kedb/engage/Slim/Slim.php(1302): Slim\Middleware\PrettyExceptions->call()
#10 /export/depts/fas/centres/kedb/engage/index.php(480): Slim\Slim->run()
#11 {main}