说明:
if else 逻辑判断
语法:
<!--{if $a == $b && $b == 1}--> a = b AND b = $b <!--{elseif $b == 2 || $a == 3}--> b = $b OR a = $a <!--{elseif $a == 1}--> a = 1 <!--{else}--> a != 1 <!--{/if}-->