There are moments when you need to see the stack trace, to know how a certain point was reached. There are two native functions for that in PHP: debug_backtrace() si debug_print_backtrace. The first one returns an array and the second will print the stack trace to the screen.

The problem is that this functions must be customized for Magento, because it is very possible that when you’re running debug_backtrace()  you can run out of memory before you can send the output to a log file.

Magento has a native function for that purpose: Varien_Debug::backtrace([bool $return = false], [bool $html = true], [bool $withArgs = true]). In order to send the resulting stacktrace to a log file you simply all it with:

1Mage::log(Varien_Debug::backtrace(true, false));

This technique is very useful when you need to see where an certain object is initialized, and what methods were executed up to that point.

In one of my adventures in the Magento code. I’ve encountered the following problem: I had to add a link to the breadcrumb.

As the documentation is not so great, after a little debugging (not a lot), I’ve got in to the core Mage_Page_Block_Html_Breadcrumbs.

The method is quite self-explanatory: addCrumb($crumbName, $crumbInfo, $after = false). Since I was there, I took a look inside:

1function addCrumb($crumbName, $crumbInfo, $after = false)
2{
3  $this->_prepareArray($crumbInfo, array('label', 'title', 'link', 'first', 'last', 'readonly'));
4  if ((!isset($this->_crumbs[$crumbName])) || (!$this->_crumbs[$crumbName]['readonly'])) {
5    $this->_crumbs[$crumbName] = $crumbInfo;
6  }
7  return $this;
8}

What’s interesting is the $after parameter, as you can see, even though it has a default value, is not used anywhere. The rest work’s as expected, probably this is why people don’t complain so much about it.