Zend::loadClass($class, $dirs) loads a PHP file
and then checks for the existance of the class.
<?php
Zend::loadClass('Container_Tree', array('/home/production/mylib', (/home/production/myapp')));
?>
After converting $class to a path hierarchy by substituting directory separators
for any underscores, the resulting hierarchy is appended to each path in $dirs
If $dirs is null, then the result will contain only the single hierarchy.
For example, Container_Tree becomes Container/Tree.php.
If /home/production/mylib/Container/Tree.php exists, then it will be included.
If not, then /home/production/myapp/Container/Tree.php will be included, if it exists.
Otherwise, PHP's include path will be searched for Container/Tree.php.
If $dirs is a string or an array, the directories are searched
in the order supplied, and the first matching file will be included.
If the file does not exist in the calculated $dirs, then PHP's include_path
will be used by the include statement (i.e. include 'Tree.php').
If the file is not found or the class does not exist after the load, a Zend_Exception is
thrown. Zend::loadFile() is used for loading, so the class name may only contain alphanumeric
characters and the hyphen ('-'), underscore ('_'), and period ('.').