Set application root absolute path in magento

If you want to change the path of magento core application folder, then you can set it as:

Mage::setRoot('/path/to/your/app');

If you look into app/Mage.php you will find that function.

    /**
     * Set application root absolute path
     *
     * @param string $appRoot
     * @throws Mage_Core_Exception
     */
    public static function setRoot($appRoot = '')
    {
        if (self::$_appRoot) {
            return ;
        }
 
        if ('' === $appRoot) {
            // automagically find application root by dirname of Mage.php
            $appRoot = dirname(__FILE__);
        }
 
        $appRoot = realpath($appRoot);
 
        if (is_dir($appRoot) and is_readable($appRoot)) {
            self::$_appRoot = $appRoot;
        } else {
            self::throwException($appRoot . ' is not a directory or not readable by this user');
        }
    }