src/Provider/GeoTIFF/GeoTIFFReader.php
protected function goToIFDEntries()
    {
        fseek($this->FileResource, 4);

        $ifdOffsetFormat = $this->isLittleEndian() ? 'VIFDoffset' : 'NIFDoffset';
        $data = unpack($ifdOffsetFormat, fread($this->FileResource, 4));

        fseek($this->FileResource, $data['IFDoffset']);
    }
protected function goToIFDEntries()
    {
        fseek($this->FileResource, 4);

        $ifdOffsetFormat = $this->isLittleEndian() ? 'VIFDoffset' : 'NIFDoffset';
        $data = unpack($ifdOffsetFormat, fread($this->FileResource, 4));

        fseek($this->FileResource, $data['IFDoffset']);
    }
The remaining 4 bytes in the header are the offset to the IFD.