Parse error: syntax error, unexpected '/' in line 728

I am getting error for the line " /core/session/manager->start();"

Please advise for any solution for this error.

// Start session and prepare global $SESSION, $USER.
if (empty($CFG->sessiontimeout)) {
    $CFG->sessiontimeout = 7200;
}
 /core/session/manager->start();

// Set default content type and encoding, developers are still required to use
// echo $OUTPUT->header() everywhere, anything that gets set later should override these headers.
// This is intended to mitigate some security problems.
if (AJAX_SCRIPT) {
    if (!core_useragent->supports_json_contenttype()) {
        // Some bloody old IE.
        @header('Content-type: text/plain; charset=utf-8');
        @header('X-Content-Type-Options: nosniff');
    } else if (!empty($_FILES)) {
        // Some ajax code may have problems with json and file uploads.
        @header('Content-type: text/plain; charset=utf-8');
    } else {
        @header('Content-type: application/json; charset=utf-8');
    }
} else if (!CLI_SCRIPT) {
    @header('Content-type: text/html; charset=utf-8');
}