Is_writeable function bug

: This article mainly introduces the bug issue of the is_writeable function. if you are interested in the PHP Tutorial, please refer to it. [Question] PHP's is_writeable () function has a Bug and cannot accurately determine whether a directory/file can be written. please write a function to determine whether the directory/file is absolutely writable.
Level 6
[Solution] The following describes the is_really_writable function solution in CodeIgniter. for details, see function comments.
The bug has two aspects,
1. in windowns, the is_writeable () function returns false only when the file is read-only. if true is returned, the file may not be writable.
If it is a directory, create a file in the directory and open the file to determine;
If it is a file, you can test whether the file can be written by opening the file (fopen.
2. in Unix, when safe_mode is enabled in the php configuration file (safe_mode = on), is_writeable () is also unavailable.
Whether to enable safe_mode when reading the configuration file.

/** * Tests for file writability * * is_writable() returns TRUE on Windows servers when you really can't write to * the file, based on the read-only attribute.  is_writable() is also unreliable * on Unix servers if safe_mode is on. * * @access  private * @return  void */if ( ! function_exists('is_really_writable')){    functionis_really_writable($file)    {// If we're on a Unix server with safe_mode off we call is_writableif (DIRECTORY_SEPARATOR == '/'AND @ini_get("safe_mode") == FALSE)        {            return is_writable($file);        }        // For windows servers and safe_mode "on" installations we'll actually// write a file then read it.  Bah...if (is_dir($file))        {            $file = rtrim($file, '/').'/'.md5(mt_rand(1,100).mt_rand(1,100));            if (($fp = @fopen($file, FOPEN_WRITE_CREATE)) === FALSE)            {                returnFALSE;            }            fclose($fp);            @chmod($file, DIR_WRITE_MODE);            @unlink($file);            returnTRUE;        }        elseif ( ! is_file($file) OR ($fp = @fopen($file, FOPEN_WRITE_CREATE)) === FALSE)        {            returnFALSE;        }        fclose($fp);        returnTRUE;    }}

'). AddClass ('pre-numbering '). hide (); $ (this ). addClass ('Has-numbering '). parent (). append ($ numbering); for (I = 1; I <= lines; I ++) {$ numbering. append ($ ('

'). Text (I) ;}; $ numbering. fadeIn (1700) ;}) ;}; script

The above introduces the is_writeable function bug, including some content, and hope to be helpful to friends who are interested in PHP tutorials.