How can I read XMP data from a JPG with PHP?

XMP data is literally embedded into the image file so can extract it with PHP's string-functions from the image file itself.

The following demonstrates this procedure (I'm using SimpleXML but every other XML API or even simple and clever string parsing may give you equal results):

$content = file_get_contents($image);$xmp_data_start = strpos($content, '<x:xmpmeta');$xmp_data_end   = strpos($content, '</x:xmpmeta>');$xmp_length     = $xmp_data_end - $xmp_data_start;$xmp_data       = substr($content, $xmp_data_start, $xmp_length + 12);$xmp            = simplexml_load_string($xmp_data);

Just two remarks:

• XMP makes heavy use of XML namespaces, so you'll have to keep an eye on that when parsing the XMP data with some XML tools.
• considering the possible size of image files, you'll perhaps not be able to use file_get_contents() as this function loads the whole image into memory. Using fopen() to open a file stream resource and checking chunks of data for the key-sequences <x:xmpmeta and </x:xmpmeta> will significantly reduce the memory footprint.

I'm only replying to this after so much time because this seems to be the best result when searching Google for how to parse XMP data. I've seen this nearly identical snippet used in code a few times and it's a terrible waste of memory. Here is an example of the fopen() method Stefan mentions after his example.

<?phpfunction getXmpData($filename, $chunkSize){    if (!is_int($chunkSize)) {        throw new RuntimeException('Expected integer value for argument #2 (chunkSize)');    }    if ($chunkSize < 12) {        throw new RuntimeException('Chunk size cannot be less than 12 argument #2 (chunkSize)');    }    if (($file_pointer = fopen($filename, 'r')) === FALSE) {        throw new RuntimeException('Could not open file for reading');    }    $startTag = '<x:xmpmeta';    $endTag = '</x:xmpmeta>';    $buffer = NULL;    $hasXmp = FALSE;    while (($chunk = fread($file_pointer, $chunkSize)) !== FALSE) {        if ($chunk === "") {            break;        }        $buffer .= $chunk;        $startPosition = strpos($buffer, $startTag);        $endPosition = strpos($buffer, $endTag);        if ($startPosition !== FALSE && $endPosition !== FALSE) {            $buffer = substr($buffer, $startPosition, $endPosition - $startPosition + 12);            $hasXmp = TRUE;            break;        } elseif ($startPosition !== FALSE) {            $buffer = substr($buffer, $startPosition);            $hasXmp = TRUE;        } elseif (strlen($buffer) > (strlen($startTag) * 2)) {            $buffer = substr($buffer, strlen($startTag));        }    }    fclose($file_pointer);    return ($hasXmp) ? $buffer : NULL;}

A simple way on linux is to call the exiv2 program, available in an eponymous package on debian.

$ exiv2 -e X extract image.jpg

will produce image.xmp containing embedded XMP which is now yours to parse.