Hie all, please help I am getting this error:

Cannot send headers; headers already sent in /home/chacks/public_html/demo2/app/Mage.php, line 767

Trace:
#0 /home/chacks/public_html/demo2/lib/Zend/Controller/Response/Abstract.php(115): Zend_Controller_Response_Abstract->canSendHeaders(true)
#1 /home/chacks/public_html/demo2/app/code/core/Mage/Core/Model/App.php(1246): Zend_Controller_Response_Abstract->setHeader('Content-Type', 'text/html; char...')
#2 /home/chacks/public_html/demo2/app/code/core/Mage/Core/Controller/Varien/Front.php(80): Mage_Core_Model_App->getResponse()
#3 /home/chacks/public_html/demo2/app/code/core/Mage/Core/Controller/Varien/Router/Standard.php(202): Mage_Core_Controller_Varien_Front->getResponse()
#4 /home/chacks/public_html/demo2/app/code/core/Mage/Core/Controller/Varien/Front.php(172): Mage_Core_Controller_Varien_Router_Standard->match(Object(Mage_Core_Controller_Request_Http))
#5 /home/chacks/public_html/demo2/app/code/core/Mage/Core/Model/App.php(354): Mage_Core_Controller_Varien_Front->dispatch()
#6 /home/chacks/public_html/demo2/app/Mage.php(684): Mage_Core_Model_App->run(Array)
#7 /home/chacks/public_html/demo2/index.php(87): Mage::run('', 'store')
#8 {main}

help please!!

If i put the credit card details wrong or payment declined by the bank on credit card order status will be changed to completed in system and order confirmation emails were sending to customer.

The demo website http://groupon.io seems be offline.

header function is not working, i've redirect to other url using CI's redirect() but it's do nothing and remains on same page,

header("Location:foo.php")
this is also do the same it's not redirecting to any other page,
Note : i am customizing the Vendor/application

Salam,

Today, I downloaded Groupon Clone application of yours from Github.

I saw an Vendor name folder it.
Can you please help me how to configure vendor management to magento since I'm not an developer?

Kindly, let me know if in case it might be time consuming for you to help in this matter. It's Ok! But anyhow I wait for your response.

It will help me a lot if this Vendor module solves my biggest tension.

Thanks in Advance
Amit Gupta