Does armor vs physical and types of ele stack?

Does armor vs physical and types of ele stack?

I've hard that for example ele armor of +15 vs fire, or any type of armor +7 vs phsycial etc do not stack.

Does this mean that wearing the same hydro, pyro, or using a weapon with this type of armor is no good if you already have?

Somebody please confirm.

They do stack if u mean as in they both take effect, but they cant both occur at the same time, so if say i have a pyromancer armour and a sword with +7 def vs physical, i take fire dmg, the dmg IS reduced by the extra +15 from the armour but the +7 has no effect at this time. however if in the same gear ur atked by a war the +7 from the sword reduces some of the dmg but the +15 from the armour does nothing.

EDIT: read the dmg explained article here http://www.gwonline.net/page.php?p=157
itll tell u about how armour works, if u want a straight answer, yes, hydromancers/pyromancers armour (or any others of the kind) do stack