为什么会出现权限被拒绝但仍成功打开文件的警告?

但是,尽管显示了警告消息,我的PHP脚本还是成功地打开了该文件,并在其中写入了一个字符串。这没有道理。

那又有什么关系呢?我可以在fopen()前面加一个@,但这仍然很奇怪,我想知道PHP为什么会这样。是否有我没有正确配置的内容?

class XMLDB {

    private $file = null;
    private $xml = null;
    private $defs = array();
    private $recs = array();

    // private members above, public members below

    public function __construct($xmlfile) {
        if (!file_exists($xmlfile)) {
            die('XML file does not exist.');
        }
        $this -> file = $xmlfile;
        $this -> xml = simplexml_load_file($this -> file);
        $this -> iniVocab();
        $this -> iniData();
    }

... /* 很多私人和公共的功能*/

    public function commit() {
        $xmlfile = fopen($this -> file, 'w'); // this is causing the warning
        $doc = new DOMDocument('1.0');
        $doc -> preserveWhiteSpace = false;
        $doc -> loadXML($this -> xml -> asXML());
        $doc -> formatOutput = true;
        fwrite($xmlfile, $doc->saveXML());
    }

    public function __destruct() {
        $this -> commit();
        /* comment this line out and there won't be any warnings, 
        /* therefore it should trace back to here. So I found out that
        /* it's when I use die() that eventually calls __destruct()
        /* which in turn calls commit() to trigger this fopen warning. */
    }
}

编辑:所以每次我尝试向打开的文件写入内容时,都没关系。然后,如果该类在卸载页面时再次尝试提交对文件的所有更改,即要销毁的对象,它将调用u destruct()方法和$this->commit()将更改写入文件-发生错误时,它拒绝写入文件并弹出“权限被拒绝”消息。真奇怪。