This question already has an answer here:

After installation of SUPEE-10415 patch on, an error is shown after flushing the Magento cache:

There has been an error processing your request

Cannot send headers; headers already sent in /home/youngag/public_html/magento/app/code/core/Mage/Core/Model/Config.php, line 1245

#0 /home/youngag/public_html/magento/lib/Zend/Controller/Response/Abstract.php(115): Zend_Controller_Response_Abstract->canSendHeaders(true)
#1 /home/youngag/public_html/magento/app/code/core/Mage/Core/Model/App.php(1246): Zend_Controller_Response_Abstract->setHeader('Content-Type', 'text/html; char...')
#2 /home/youngag/public_html/magento/app/code/core/Mage/Core/Controller/Varien/Front.php(80): Mage_Core_Model_App->getResponse()
#3 /home/youngag/public_html/magento/app/code/core/Mage/Core/Model/Url/Rewrite.php(204): Mage_Core_Controller_Varien_Front->getResponse()
#4 /home/youngag/public_html/magento/app/code/core/Mage/Core/Controller/Varien/Front.php(166): Mage_Core_Model_Url_Rewrite->rewrite()
#5 /home/youngag/public_html/magento/app/code/core/Mage/Core/Model/App.php(354): Mage_Core_Controller_Varien_Front->dispatch()
#6 /home/youngag/public_html/magento/app/Mage.php(683): Mage_Core_Model_App->run(Array)
#7 /home/youngag/public_html/magento/index.php(93): Mage::run('', 'store')
#8 {main}

Has anyone else encountered this error? Any insight as to how to solve this issue would be appreciated.

marked as duplicate by 7ochem, Jai, Manoj Deswal, Dhiren Vasoya, Manashvi Birla Apr 20 '18 at 5:08

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.


check your excpetions log for the following message:

"exception 'Exception' with message 'Unsupported data type N' in /var/www/src/lib/Unserialize/Reader/ArrValue.php:88 Stack trace: .."

If you get this one, then most likely the Patch 8788v2 has not been applied. The files solving the issue are: /lib/Unserialize/Parser.php /lib/Unserialize/Reader/Arr.php /lib/Unserialize/Reader/ArrValue.php /lib/Unserialize/Reader/Null.php

Expcially if you are missing the /lib/Unserialize/Reader/Null.php file it means the patch has not been applied.

Greet axe

  • Thank you. I'm afraid that's not the issue however. The patch was previously applied and /lib/Unserialize/Reader/Null.php is in place. – jpluttme Apr 20 '18 at 17:16
  • Log files seem to indicate an issue with lib/Varien/Simplexml/Config.php, specifically: XML declaration allowed only at the start of the document on line 510 which is: $xml = simplexml_load_string($string, $this->_elementClass); – jpluttme Apr 20 '18 at 17:21
  • Does your page load when you clear your cache? And then it crashes when you reload? – axe1987 Apr 20 '18 at 17:35
  • If this is the case then check all module XML files for valid XML. There can also be a faulty config entry in your core_config_data. Look for a key with a number like somekey/2/subkey – axe1987 Apr 20 '18 at 17:43

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