标签：

1，执行Linux命令 <?php $a =`ls -a /`; // execute linux command echo '<pre>'.$a; 2.为变量起别号 <?php $a = 2; $b =&$a; //为$a起别号 echo $b; //2 $a = 4; echo $b;//4 unset($a); // $b = 6; echo $b; //6 3. 数组运算。+，， ==， ===， !=, <>, !== <?php $a = [1,2,3]; $b = [4,2,3]; print_r($a+$b); print_r($b+$a);

PHP 冷常识