$a = 1;
if($a == 1) {
$b = $a;
} else {
$b = 2;
}
$b = $a==1 ? $a : 2;
@$num = 100/0;
三元运算符， @屏蔽错误运算符
原文：https://www.cnblogs.com/big2cat/p/9855478.html
