#### 1. 三元運(yùn)算符語(yǔ)法糖總結(jié) --- 三元運(yùn)算符的簡(jiǎn)化形式 ``` $a ?: 0 等同于 $a ? $a : 0 $a ?? 0 等同于 isset($a) ? $a : 0 ``` #### 2. PHP5.3.0 引入 ?: --- PHP5.3.0 更新公告 : [https://www.php.net/releases/5_3_0.php](https://www.php.net/releases/5_3_0.php) ![](https://img.itqaq.com/art/content/b1963bb17fbfec5bc5c4f29857a87140.png) #### 3. PHP7.0.0 引入 ?? (NULL 合并運(yùn)算符) --- PHP7.0 新特性 [https://www.php.net/manual/zh/migration70.new-features.php](https://www.php.net/manual/zh/migration70.new-features.php) ![](https://img.itqaq.com/art/content/8a8406c0d40ac0bf226450a141323204.png)