Fehler bei der Installation von Woltlab Forum 5.1.9

class GZipFile extends File {
    /**
     * checks if gz*64 functions are available instead of gz*
     * https://bugs.php.net/bug.php?id=53829
     * @var    boolean
     */
    protected static $gzopen64 = null;
    
    /** @noinspection PhpMissingParentConstructorInspection */
    /**
     * Opens a gzip file.
     * 
     * @param    string        $filename
     * @param    string        $mode
     * @throws    SystemException
     */
    public function __construct($filename, $mode = 'wb') {
        if (self::$gzopen64 === null) {
            self::$gzopen64 = function_exists('gzopen64');
        }
        
        $this->filename = $filename;
        /** @noinspection PhpUndefinedFunctionInspection */
        $this->resource = (self::$gzopen64 ? gzopen64($filename, $mode) : gzopen($filename, $mode));
        if ($this->resource === false) {
            throw new SystemException('Can not open file ' . $filename);
        }
    }
    
    /**
     * Calls the specified function on the open file.
     * 
     * @param    string        $function
     * @param    array        $arguments
     * @return    mixed
     * @throws    SystemException
     */
    public function __call($function, $arguments) {
        if (self::$gzopen64 && function_exists('gz' . $function . '64')) {
            array_unshift($arguments, $this->resource);
            return call_user_func_array('gz' . $function . '64', $arguments);
        }
        else if (function_exists('gz' . $function)) {
            array_unshift($arguments, $this->resource);
            return call_user_func_array('gz' . $function, $arguments);
        }
        else if (function_exists($function)) {
            array_unshift($arguments, $this->filename);
            return call_user_func_array($function, $arguments);
        }
        else {
            throw new SystemException('Can not call method ' . $function);
        }
    }
    
    /**
     * Returns the filesize of the unzipped file.
     * 
     * @return    integer
     */
    public function getFileSize() {
        $byteBlock = 1<<14;
        $eof = $byteBlock;
        
        // the correction is for zip files that are too small
        // to get in the first while loop
        $correction = 1;
        while ($this->seek($eof) == 0) {
            $eof += $byteBlock;
            $correction = 0;
        }
        
        while ($byteBlock > 1) {
            $byteBlock >>= 1;
            $eof += $byteBlock * ($this->seek($eof) ? -1 : 1);
        }
        
        if ($this->seek($eof) == -1) $eof--;
        
        $this->rewind();
        return $eof - $correction;
    }
}