Why is frontend of Magento site not loading up? - Fatal error: Class ‘Mage__Helper_Data’ not found

I’ve got an issue with the front end of a magento site, it is throwing a 500 error. The back end admin is absolutely fine and functional, I'm able to log in no problem and there is no loss of product data.

I have un-commented out line 70 in my index.php file -

#ini_set(\'display_errors\', 1);

in order to see the errors, and this is what now displays when you load up the front end of the site - Fatal error: Class \’Mage__Helper_Data\’ not found in /var/www/vhosts/beta.mydomain.com/httpdocs/countrytoys/app/Mage.php on line 520

I reckon the double underscore here is to do with a module being missing or something..

This problem came to light after I refreshed all cache types in the admin area, but I suspect the problem was there beforehand but just bared it’s head after the cache refresh.

So far I have tried/checked -

• deleting the contents of var/cache, var/session

• The base URL in the db is correct

• made all directories 755 permissions, and all files 644, I have also tried making index.php 755, and 777 on suggestion from other forums.

• checked htaccess, all seems fine.

• the physical files are all there on the server.

• system.log seems to be consistently pointing to line 93 in Autoload.php -

  2011-09-12T15:18:52+00:00 ERR (3): Warning: include() [<a href=\'function.include\'>function.include</a>]: Failed opening \'Mage//Helper/Data.php\' 开发者_StackOverflow中文版for inclusion (include_path=\'/var/www/vhosts/beta.mydomain.com/httpdocs/countrytoys/app/code/local:/var/www/vhosts/beta.mydomain.com/httpdocs/countrytoys/app/code/community:/var/www/vhosts/beta.mydomain.com/httpdocs/countrytoys/app/code/core:/var/www/vhosts/beta.mydomain.com/httpdocs/countrytoys/lib:.:\')  in /var/www/vhosts/beta.mydomain.com/httpdocs/countrytoys/lib/Varien/Autoload.php on line 93
  

Other things I can think of that I have recently done include adding google analytics through admin, altering the code for links at the top of the site in app\design\frontend\default\blue_toys\template\page\html\header.phtml and entering some paypal details in order to set up the payment gateway.

installation details - ver -1.5.0.1, Theme - custom installed theme

Can anyone help? thanks, Luke

---

Your error message shows two underscores between Mage and Helper, where there usually is only one of them. For me it looks like you lost a word between Mage and Helper somewhere, as usually Mage helper identifiers are s/t like Mage_Core_Helper_Data.

I'd check the <helpers> sections of my /etc/config.xml files for wrong definitions first.

Other than that I'd probably try to get a debug trace inside the Varien_Autoload::autoload method.

I'd lookout for patterns in the parameter $class which could result in s/t like Mage__Helper_Data, e.g. occurences where $class contains spaces or double underscores:

public function autoload($class)
{

    try {
        if (strpos($class, ' ') !== false || strpos($class, '__') !== false) {
            throw new Exception('fishy');
        }
    }
    catch (Exception $e) {
        var_dump($class, $e->getTraceAsString());
        die('stop');
    }

    // original method code starts here
    // :

}

---

I had a similar problem, and this question appeared in the Google results, so I thought it would be sensible to add an answer here for anyone else struggling with the same problem. With my issue, it was related to a custom <source_model> I was trying to use in the Magento configuration system.

I used the example code from Magento, which looks like this:

public function toOptionArray()
    {
        return array(
            array('value' => 0, 'label' => Mage::helper()->__('First item')),
            array('value' => 1, 'label' => Mage::helper()->__('Second item')),
            array('value' => 2, 'label' => Mage::helper()->__('third item'))
        );
    }

The error was coming from the Mage::helper() bit - no helper was being loaded. You can change it to this, or load a specific helper:

public function toOptionArray()
    {
        return array(
            array('value' => 0, 'label' => 'First item'),
            array('value' => 1, 'label' => 'Second item'),
            array('value' => 2, 'label' => 'third item')
        );
    }