php - Set Error Message Once Per Page Request -

i'm trying create minimum total checkout module prevent checking out total less configurable amount.

i'm using event sales_quote_save_before display error on checkout/cart page when it's opened.

<?xml version="1.0"?> <config>     <frontend>         <events>             <sales_quote_save_before>                 <observers>                     <b2b>                         <class>b2b/observer</class>                         <method>checktotalscart</method>                     </b2b>                 </observers>             </sales_quote_save_before>         </events>     </frontend> </config> 

and in observer

public function checktotalscart() {     if ($this->_hascarterror()) { /* checks, returns bool */         $this->_seterrormessage();     } } protected function _seterrormessage() {     $session = mage::getsingleton("b2b/session"); /* extends mage_core_model_session */     $session->adderror($this->helper->geterrormessage()); } 

the problem when update cart cart page, error message showing twice. guess event happening multiple times.

i've tried check if message set custom session variable

protected function _seterrormessage() {     $session = mage::getsingleton("b2b/session");     if ($session->haserrormessage()) {         return;     }     $session->adderror($this->helper->geterrormessage());     $session->haserrormessage(true); } 

but didn't work either. how can make sure error message showing once per page request?

you must use $session->seterrormessage(true); instead of $session->haserrormessage(true);, isset()shortcut (both magic methods, can check varien_object::__call() see what's behaviour).

but message displayed once per session, detect if message added using code :

protected function _seterrormessage() {     $session = mage::getsingleton('b2b/session'); /* extends mage_core_model_session */     $errormessage = $this->helper->geterrormessage();     $ismessageadded = false;      foreach ($session->getmessages() $message) {         if ($message->gettext() == $errormessage) {             $ismessageadded = true;             break;         }     }     if (!$ismessageadded) {         $session->adderror($errormessage);     }      return $this; }