How to display thumbnails in it's original size with PHP

By default, the /2/files/get_thumbnail endpoint will return a 64x64 thumbnail of the requested image. If you want a different size, you can request it using the "size" parameter. You can specify that the same way you specify the "mode" and "format" parameters. You can find more information, such as the sizes that are available, in the /2/files/get_thumbnail:

https://www.dropbox.com/developers/documentation/http/documentation#files-get_thumbnail

Note that if you want the original file data though, you can instead use /2/files/download:

https://www.dropbox.com/developers/documentation/http/documentation#files-download

Problem solved!! 

I read a little further the documentation I figured out that I was missing the paramenter size on my code.

So I changed this line:

curl_setopt($ch, CURLOPT_HTTPHEADER, array('Authorization: Bearer ' . $token[0]->itoken, 'Dropbox-API-Arg: {"path": "/test-1/Capture-desktop.PNG", "format": "png", "mode": "strict"}'));

For this one:

    curl_setopt($ch, CURLOPT_HTTPHEADER, array('Authorization: Bearer ' . $token[0]->itoken, 'Dropbox-API-Arg: {"path": "/test-1/Capture-desktop.PNG", "format": "png", "size": "w1024h768", "mode": "strict"}'));

The size options I found in this link: https://www.dropbox.com/developers/documentation/http/documentation#files-get_thumbnail

And now it's working perfectly!

Cheers!!