empty 和 isset 区别，emptyisset区别

<?<span>php

</span><span>/*</span><span>*
*    isset  &mdash; 检测变量是否设置
*    如果 变量 存在则返回 true， 否则返回 false
*
*    empty  &mdash; 检查一个变量是否为空
*    如果 变量 是非空或非零的值，则 empty() 返回 false
*</span><span>*/</span>

<span>$is_var</span> = ''<span>;

</span><span>if</span>(<span>isset</span>(<span>$is_var</span><span>)) {
    </span><span>echo</span> "变量存在！<br />"<span>;
} </span><span>else</span><span> {
    </span><span>echo</span> "变量不存在！<br />"<span>;
}

</span><span>if</span>(<span>empty</span>(<span>$is_var</span><span>)) {
    </span><span>echo</span> "变量为空！<br />"<span>;
} </span><span>else</span><span> {
    </span><span>echo</span> "变量不为空！<br />"<span>;
}

</span>?>