循環數組引用傳值時,刪除元素不要直接unset($v),而是unset($arr[$key]) 兩個數組都用$v,但是只有第一個數組引用傳值 ``` $arr = array("a", "b", "c"); $arr2 = array("d", "e", "f"); foreach($arr as &$v) { $v .= 1; } var_dump($arr);//array ( 0 => 'a1', 1 => 'b1', 2 => 'c1', ) var_dump($arr2);//array ( 0 => 'd', 1 => 'e', 2 => 'f', ) foreach($arr2 as $v) { $v .= 2; } var_dump($arr);//array ( 0 => 'a1', 1 => 'b1', 2 => 'f2', ) var_dump($arr2);//array ( 0 => 'd', 1 => 'e', 2 => 'f', ) ``` 所以這種情況我們需要再第一個數組循環后unset($v);以免影響到下一個 又或者將后面的循環放到函數里 兩個數組都用$v且都引用傳值 ``` $arr = array("a", "b", "c"); $arr2 = array("d", "e", "f"); foreach($arr as &$v) { $v .= 1; } var_dump($arr);//array ( 0 => 'a1', 1 => 'b1', 2 => 'c1', ) var_dump($arr2);//array ( 0 => 'd', 1 => 'e', 2 => 'f', ) foreach($arr2 as &$v) { $v .= 2; } var_dump($arr);//array ( 0 => 'a1', 1 => 'b1', 2 => 'c1', ) var_dump($arr2);//array ( 0 => 'd2', 1 => 'e2', 2 => 'f2', ) ```