取消设置对象变量'；的属性，影响了其在父作用域中的值

我制作了一个小库来读取数据库导出的xml文件，并将其输出为结构化关联数组。它还可以按表列筛选输出。

完成代码后，当我玩这个类时，我会发现一些奇怪的东西。unset的作用就好像该变量是通过引用传递的一样。

我找不到任何可能的错误，所以我提出了设置$this->rows的特定方法，希望有人能照亮我。

private function populateData($rowLimit)
    {
        if (!$this->getColumns()) {
            throw new ReaderException(__FUNCTION__ . " # Unable to get columns name.");
        }
        // database->tableName->rows
        $rows = $this->getSimpleXmlElement()->children()->children();
        if ($this->getFilteredColumns()) {
            $toRemoves = array_values(array_diff($this->getColumns(),
                $this->getFilteredColumns()));
            foreach ($rows as $row) {
                foreach ($toRemoves as $toRemove) {
                    unset($row->{$toRemove});
                }
            }
        }
        $rows = $this->simpleXmlToArray($rows)['row'];
        if ($rowLimit) {
            $limited = [];
            for ($i = 0; $i < $rowLimit; $i++) {
                $limited[] = $rows[$i];
            }
            $this->setRows($limited);
        } else {
            $this->setRows($rows);
        }
        $structArray = [
            'database' => $this->getDatabaseName(),
            'table' => $this->getTableName(),
            'columns' => !$this->getFilteredColumns() ? $this->getColumns()
                : $this->getFilteredColumns(),
            'rows' => $this->getRows()
        ];
        $this->setStruct($structArray);
        return $this;
    }

$xml = new SomeXmlReader($companyTableFilePath);
$xml->get(1);

输出：

[
 "database" => "myDatabase",
 "table" => "companies",
 "columns" => [
   "id",
   "name",
   "license_no",
   "phone",
   "created",
   "modified",
 ],
 "rows" => [
   [
     "id" => "1",
     "name" => "SOME COMPANY NAME",
     "license_no" => "884652",
     "phone" => null,
     "created" => "2015-09-25 16:01:57",
     "modified" => "2015-09-25 16:01:57",
   ],
 ],
]

当我试图过滤掉一些列时，我会进行

$xml->setFilteredColumns(['id','name'])->get(1);

它按预期返回结果：列已被修剪。输出：

[
 "database" => "myDatabase",
 "table" => "companies",
 "columns" => [
   "id",
   "name",
 ],
 "rows" => [
   [
     "id" => "1",
     "name" => "SOME COMPANY NAME",
   ],
 ],
]

然而，就在这条线之后，当我用再次测试它时

$xml->setFilteredColumns(['id','name','phone'])->get(1);

在下一行，出了问题。输出为：

[
 "database" => "myDatabase",
 "table" => "companies",
 "columns" => [
   "id",
   "name",
   "phone",
 ],
 "rows" => [
   [
     "id" => "1",
     "name" => "SOME COMPANY NAME",
   ],
 ],
]

经过追踪，发现$this->getSimpleXmlElement()已被unset修饰。在这个应用程序生命周期内，我再也无法获得$this->getSimpleXmlElement()的完整/原始值。

是我犯了一个根本性的错误，还是这是PHP语言的行为？