php代码这样写是不是多此一举？？-PHP Tutorial-php.cn

php代码这样写是不是多此一举？？

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Release： 2016-06-06 20:19:32

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<code>class PHPExcel_Shared_File
{
protected static $_useUploadTempDirectory    = FALSE;
public static function sys_get_temp_dir()
    {
        if (self::$_useUploadTempDirectory) {
            //  use upload-directory when defined to allow running on environments having very restricted
            //      open_basedir configs
            if (ini_get('upload_tmp_dir') !== FALSE) {
                if ($temp = ini_get('upload_tmp_dir')) {
                    if (file_exists($temp))
                        return realpath($temp);
                }
            }
        }

        // sys_get_temp_dir is only available since PHP 5.2.1
        // http://php.net/manual/en/function.sys-get-temp-dir.php#94119
        if ( !function_exists('sys_get_temp_dir')) {
            if ($temp = getenv('TMP') ) {
                if ((!empty($temp)) && (file_exists($temp))) { return realpath($temp); }
            }
            if ($temp = getenv('TEMP') ) {
                if ((!empty($temp)) && (file_exists($temp))) { return realpath($temp); }
            }
            if ($temp = getenv('TMPDIR') ) {
                if ((!empty($temp)) && (file_exists($temp))) { return realpath($temp); }
            }

            // trick for creating a file in system's temporary dir
            // without knowing the path of the system's temporary dir
            $temp = tempnam(__FILE__, '');
            if (file_exists($temp)) {
                unlink($temp);
                return realpath(dirname($temp));
            }

            return null;
        }

        // use ordinary built-in PHP function
        //    There should be no problem with the 5.2.4 Suhosin realpath() bug, because this line should only
        //        be called if we're running 5.2.1 or earlier
        return realpath(sys_get_temp_dir());
    }

}
｝</code>

Copy after login

这是摘出来的一段代码。两个问题
1：protected static $_useUploadTempDirectory = FALSE; 恒假，那么if (self::$_useUploadTempDirectory)这个判断就不成立，为什么还要写这个if语句呢？

2:if ( !function_exists('sys_get_temp_dir')) 这个if语句就在sys_get_temp_dir函数中，也就是说这个函数一直存在啊？？那么下面的语句也就不会执行了啊

不知道我理解的对不对？？这个也算是一个比较成熟的cms里的代码了。。为什么会这么写呢？？

回复内容：

<code>class PHPExcel_Shared_File
{
protected static $_useUploadTempDirectory    = FALSE;
public static function sys_get_temp_dir()
    {
        if (self::$_useUploadTempDirectory) {
            //  use upload-directory when defined to allow running on environments having very restricted
            //      open_basedir configs
            if (ini_get('upload_tmp_dir') !== FALSE) {
                if ($temp = ini_get('upload_tmp_dir')) {
                    if (file_exists($temp))
                        return realpath($temp);
                }
            }
        }

        // sys_get_temp_dir is only available since PHP 5.2.1
        // http://php.net/manual/en/function.sys-get-temp-dir.php#94119
        if ( !function_exists('sys_get_temp_dir')) {
            if ($temp = getenv('TMP') ) {
                if ((!empty($temp)) && (file_exists($temp))) { return realpath($temp); }
            }
            if ($temp = getenv('TEMP') ) {
                if ((!empty($temp)) && (file_exists($temp))) { return realpath($temp); }
            }
            if ($temp = getenv('TMPDIR') ) {
                if ((!empty($temp)) && (file_exists($temp))) { return realpath($temp); }
            }

            // trick for creating a file in system's temporary dir
            // without knowing the path of the system's temporary dir
            $temp = tempnam(__FILE__, '');
            if (file_exists($temp)) {
                unlink($temp);
                return realpath(dirname($temp));
            }

            return null;
        }

        // use ordinary built-in PHP function
        //    There should be no problem with the 5.2.4 Suhosin realpath() bug, because this line should only
        //        be called if we're running 5.2.1 or earlier
        return realpath(sys_get_temp_dir());
    }

}
｝</code>

Copy after login

2:if ( !function_exists('sys_get_temp_dir')) 这个if语句就在sys_get_temp_dir函数中，也就是说这个函数一直存在啊？？那么下面的语句也就不会执行了啊

不知道我理解的对不对？？这个也算是一个比较成熟的cms里的代码了。。为什么会这么写呢？？

1 static 只是静态，但是可以被修改的
2 sys_get_temp_dir 指的是php系统自带的函数，而不是类中的函数

有没有想过，它的继承类可能把$_useUploadTempDirectory设成true？