View file smarty/sysplugins/smarty_internal_compile_debug.php

<?php 
/**
* Smarty Internal Plugin Compile Debug
*
* Compiles the {debug} tag 
* It opens a window the the Smarty Debugging Console
* @package Smarty
* @subpackage Compiler
* @author Uwe Tews
*/
/**
* Smarty Internal Plugin Compile Debug Class
*/ 
class Smarty_Internal_Compile_Debug extends Smarty_Internal_CompileBase {
    /**
    * Compiles code for the {debug} tag
    * 
    * @param array $args array with attributes from parser
    * @param object $compiler compiler object
    * @return string compiled code
    */
    public function compile($args, $compiler)
    {
        $this->compiler = $compiler; 
        // check and get attributes
        $_attr = $this->_get_attributes($args);

        // display debug template
        $_output = "<?php \$_smarty_tpl->smarty->loadPlugin('Smarty_Internal_Debug'); Smarty_Internal_Debug::display_debug(\$_smarty_tpl->smarty); ?>";
        return $_output;
    } 
} 

?>