Error log - 'PHP Fatal error: Class 'Mage_Catalog_Model_Product' not found in'

Question

One of our clients is running a Magento site that experiences intermittent problems where the home-page half-loads occasionally.

Investigating /var/log/httpd/error_log reveals the following which appears to be the source of the problem:

[Sat Feb 28 21:05:45 2015] [error] [client ###.###.#.###] PHP Fatal error:  Class 'Mage_Catalog_Model_Product' not found in /var/www/html/app/code/local/TM/Highlight/Block/Product/Abstract.php on line 40

The culprit code block in /local/TM/Highlight/Block/Product/Abstract.php is:

    $this->addData(array(
        'cache_lifetime'    => 86400,
        'cache_tags'        => array(Mage_Catalog_Model_Product::CACHE_TAG),
    ));

I've had a quick look at the documentation for the Mage_Catalog_Model_Product class and it does seem that class exists and so does the constant CACHE_TAG.

What's going on here? Is it a bug in this Abstract.php (which has come from Templates-Master at http://www.templates-master.com)? Is the Mage_Catalog_Model_Product class magically being loaded sometimes and not loaded other times for some reason?

Answer 1

Did you check if you compilation is enabled and is correctly build?

Maybe a conflict with some other installed modules? You could(on a test environment) disable some modules/cache/compilation and enable developermodus to investigate further.

Maybe you installed a module which adds some magic to the existing autoloader.