CI_Upload::_file_mime_type PHP Méthode

    protected function _file_mime_type($file)
    {
        // We'll need this to validate the MIME info string (e.g. text/plain; charset=us-ascii)
        $regexp = '/^([a-z\\-]+\\/[a-z0-9\\-\\.\\+]+)(;\\s.+)?$/';
        /* Fileinfo extension - most reliable method
         *
         * Unfortunately, prior to PHP 5.3 - it's only available as a PECL extension and the
         * more convenient FILEINFO_MIME_TYPE flag doesn't exist.
         */
        if (function_exists('finfo_file')) {
            $finfo = @finfo_open(FILEINFO_MIME);
            if (is_resource($finfo)) {
                $mime = @finfo_file($finfo, $file['tmp_name']);
                finfo_close($finfo);
                /* According to the comments section of the PHP manual page,
                 * it is possible that this function returns an empty string
                 * for some files (e.g. if they don't exist in the magic MIME database)
                 */
                if (is_string($mime) && preg_match($regexp, $mime, $matches)) {
                    $this->file_type = $matches[1];
                    return;
                }
            }
        }
        /* This is an ugly hack, but UNIX-type systems provide a "native" way to detect the file type,
         * which is still more secure than depending on the value of $_FILES[$field]['type'], and as it
         * was reported in issue #750 (https://github.com/EllisLab/CodeIgniter/issues/750) - it's better
         * than mime_content_type() as well, hence the attempts to try calling the command line with
         * three different functions.
         *
         * Notes:
         *	- the DIRECTORY_SEPARATOR comparison ensures that we're not on a Windows system
         *	- many system admins would disable the exec(), shell_exec(), popen() and similar functions
         *	  due to security concerns, hence the function_usable() checks
         */
        if (DIRECTORY_SEPARATOR !== '\\') {
            $cmd = function_exists('escapeshellarg') ? 'file --brief --mime ' . escapeshellarg($file['tmp_name']) . ' 2>&1' : 'file --brief --mime ' . $file['tmp_name'] . ' 2>&1';
            if (function_usable('exec')) {
                /* This might look confusing, as $mime is being populated with all of the output when set in the second parameter.
                 * However, we only need the last line, which is the actual return value of exec(), and as such - it overwrites
                 * anything that could already be set for $mime previously. This effectively makes the second parameter a dummy
                 * value, which is only put to allow us to get the return status code.
                 */
                $mime = @exec($cmd, $mime, $return_status);
                if ($return_status === 0 && is_string($mime) && preg_match($regexp, $mime, $matches)) {
                    $this->file_type = $matches[1];
                    return;
                }
            }
            if (!ini_get('safe_mode') && function_usable('shell_exec')) {
                $mime = @shell_exec($cmd);
                if (strlen($mime) > 0) {
                    $mime = explode("\n", trim($mime));
                    if (preg_match($regexp, $mime[count($mime) - 1], $matches)) {
                        $this->file_type = $matches[1];
                        return;
                    }
                }
            }
            if (function_usable('popen')) {
                $proc = @popen($cmd, 'r');
                if (is_resource($proc)) {
                    $mime = @fread($proc, 512);
                    @pclose($proc);
                    if ($mime !== FALSE) {
                        $mime = explode("\n", trim($mime));
                        if (preg_match($regexp, $mime[count($mime) - 1], $matches)) {
                            $this->file_type = $matches[1];
                            return;
                        }
                    }
                }
            }
        }
        // Fall back to the deprecated mime_content_type(), if available (still better than $_FILES[$field]['type'])
        if (function_exists('mime_content_type')) {
            $this->file_type = @mime_content_type($file['tmp_name']);
            if (strlen($this->file_type) > 0) {
                return;
            }
        }
        $this->file_type = $file['type'];
    }