Any one can help me to analyze this function and about plugin about 'defun'!
Thank you all the same!!!

/* create code for closing a function definition and calling said function */
function smarty_compiler_defun_close($tag_args, &$compiler) {
    list($name, $attrs, $open_tag_args, $func_key) = array_pop($compiler->_tag_stack);
    if ($name!='defun') $compiler->_syntax_error("unexpected {/defun}");
    return " $this->_tpl_vars = $_fun_tpl_vars; }} " . $func_key . smarty_compiler_fun($open_tag_args, $compiler);
}
$this->register_compiler_function('/defun', 'smarty_compiler_defun_close');

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Edit: linked to old thread; syntax highlighting activated. [Alfie]