静态变量赋值问题？-PHP Tutorial-php.cn

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静态变量赋值问题？

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Jun 23, 2016 pm 02:26 PM

$a=100;
static $b=$a;
echo $b;

请问静态变量为何不能这样赋值？

回复讨论(解决方案)

$b=100;
static $a;
$a=$b;
echo $a;

这样确可以？

静态属性只能被初始化为一个字符值或一个常量，不能使用表达式。
你可以static $a='a';或者$a=100 但是不能进行赋值运算或者其他表达式。

静态变量创建于 php 预编译期间
所以不能用普通变量赋值，因为普通变量创建于其后的运行期间

说白了就是，你不能向静态变量赋一个不存在的值

静态变量不能拿另外一个变量直接给他赋值。声明之后，才可以。

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