In elgg1.8 /mod/blog/....., I find this code: elgg_view_form('blog/save', $vars, $body_vars);

there are two  parameters(type: array): $vars , $body_vars;

but i can't find $body_vars in the blog/views/forms/blog/save.php

And my question is when i use elgg_view_form('blog/save', $vars, $body_vars);

i can use more parameters, and i can always use '$vars' to fetch the data?