React\Gifsocket\GifEncoder::encodeFrame PHP Method

    private function encodeFrame($frame, $delay)
    {
        $data = '';
        $localsStr = 13 + 3 * (2 << (ord($frame[10]) & 0x7));
        $localsEnd = strlen($frame) - $localsStr - 1;
        $localsTmp = substr($frame, $localsStr, $localsEnd);
        $globalLen = 2 << (ord($this->initialFrame[10]) & 0x7);
        $localsLen = 2 << (ord($frame[10]) & 0x7);
        $globalRgb = substr($this->initialFrame, 13, 3 * (2 << (ord($this->initialFrame[10]) & 0x7)));
        $localsRgb = substr($frame, 13, 3 * (2 << (ord($frame[10]) & 0x7)));
        $localsExt = "!ù" . chr(($this->disposal << 2) + 0) . chr($delay >> 0 & 0xff) . chr($delay >> 8 & 0xff) . "";
        if ($this->transparentColor !== null && ord($frame[10]) & 0x80) {
            for ($j = 0; $j < 2 << (ord($frame[10]) & 0x7); $j++) {
                if (ord($localsRgb[3 * $j + 0]) == ($this->transparentColor >> 16 & 0xff) && ord($localsRgb[3 * $j + 1]) == ($this->transparentColor >> 8 & 0xff) && ord($localsRgb[3 * $j + 2]) == ($this->transparentColor >> 0 & 0xff)) {
                    $localsExt = "!ù" . chr(($this->disposal << 2) + 1) . chr($delay >> 0 & 0xff) . chr($delay >> 8 & 0xff) . chr($j) . "";
                    break;
                }
            }
        }
        switch ($localsTmp[0]) {
            case "!":
                $localsImg = substr($localsTmp, 8, 10);
                $localsTmp = substr($localsTmp, 18, strlen($localsTmp) - 18);
                break;
            case ",":
                $localsImg = substr($localsTmp, 0, 10);
                $localsTmp = substr($localsTmp, 10, strlen($localsTmp) - 10);
                break;
        }
        if (ord($frame[10]) & 0x80 && null !== $this->initialFrame) {
            if ($globalLen == $localsLen) {
                if ($this->gifBlockCompare($globalRgb, $localsRgb, $globalLen)) {
                    $data .= $localsExt . $localsImg . $localsTmp;
                } else {
                    $byte = ord($localsImg[9]);
                    $byte |= 0x80;
                    $byte &= 0xf8;
                    $byte |= ord($this->initialFrame[10]) & 0x7;
                    $localsImg[9] = chr($byte);
                    $data .= $localsExt . $localsImg . $localsRgb . $localsTmp;
                }
            } else {
                $byte = ord($localsImg[9]);
                $byte |= 0x80;
                $byte &= 0xf8;
                $byte |= ord($frame[10]) & 0x7;
                $localsImg[9] = chr($byte);
                $data .= $localsExt . $localsImg . $localsRgb . $localsTmp;
            }
        } else {
            $data .= $localsExt . $localsImg . $localsTmp;
        }
        return $data;
    }