$var not greater than and not lesser than character length

Can't seem to get this to work. What Im trying to achieve is check if the variable isn't longer than 68, but also not shorter than 64.

However, I can't seem to achieve even that...can someone please point out what I'm doing wrong?

Also, is there a way to simplify this procedure?

if (!strlen($pre_session_key_1) > 68) {
            if (!strlen($pre_session_key_1) < 64) {
}
}

Thanks and please be kind newb here,