php中一个"异类"语法： $a && $b = $c;
- WBOYOriginal
- 2016-07-09 09:08:051252browse
php中一个"异类"语法： $a && $b = $c;
$a = 1;
$b = 2;
$c = 3;
$a && $b = $c;
echo "a:$a";
echo "b:$b";
echo "c:$c";
这样是
a:1
b:3
c:3
$a = 0;
$b = 2;
$c = 3;
$a && $b = $c;
echo "a:$a";
echo "b:$b";
echo "c:$c";
这样是
a:0
b:2
c:3
$b = 2;
$c = 3;
$a && $b = $c;
echo "a:$a";
echo "b:$b";
echo "c:$c";
这样是
a:1
b:3
c:3
$a = 0;
$b = 2;
$c = 3;
$a && $b = $c;
echo "a:$a";
echo "b:$b";
echo "c:$c";
这样是
a:0
b:2
c:3
解析：
1: && 和赋值运算符“=”的优先级是&&优先级高，但是加红的写法中并不是 $a和$b先做与运算然后 =$c,这么理解相当于 1=$c, 而 1=$c这样的写法是错误的
2： 这种另类的写法正确的理解方式为：
if($a){$b = $c},即如果$a为真，则执行赋值语句$b = $c;否则不执行此赋值语句，这样结果不难理解
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