$a=[1,2,3]; foreach ($a as &$v){} foreach ($a as $v){} var_dump ($a) 等于多少； php

$a=[1,2,3]; foreach ($a as &$v){} foreach ($a as $v){} var_dump ($a) 等于多少；

答案：122

解析：

$value即使在foreach循环之后 ， a和最后一个数组元素的引用仍然存在。建议通过unset()销毁它。否则，您将遇到以下行为：

參考資料

http://php.net/manual/en/control-structure...

在 Warning 中有明確指出此問題。

http://php.net/manual/en/language.references.whatdo.php

Note, however, that references inside arrays are potentially dangerous. Doing a normal (not by reference) assignment with a reference on the right side does not turn the left side into a reference, but references inside arrays are preserved in these normal assignments. This also applies to function calls where the array is passed by value.

在赋值数组的时候，如果=右边的数据存在引用，那边赋值的新数组对应的元素也是引用，所以改变$c[0]的值 也会同时改变$a[0]的值。