Code for APIv2

If you want to call the Dropbox API directly, rather than via a library, you can makes HTTPS connections to the endpoints themselves. For example, to upload a file, you would use /2/files/upload. Calling that using curl in PHP would look something like this:

    <?php

    $path = 'test_php_upload.txt';
    $fp = fopen($path, 'rb');
    $size = filesize($path);

    $cheaders = array('Authorization: Bearer <ACCESS_TOKEN>',
                      'Content-Type: application/octet-stream',
                      'Dropbox-API-Arg: {"path":"/test/'.$path.'", "mode":"add"}');

    $ch = curl_init('https://content.dropboxapi.com/2/files/upload');
    curl_setopt($ch, CURLOPT_HTTPHEADER, $cheaders);
    curl_setopt($ch, CURLOPT_PUT, true);
    curl_setopt($ch, CURLOPT_CUSTOMREQUEST, 'POST');
    curl_setopt($ch, CURLOPT_INFILE, $fp);
    curl_setopt($ch, CURLOPT_INFILESIZE, $size);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    $response = curl_exec($ch);

    echo $response;
    curl_close($ch);
    fclose($fp);

    ?>

`<ACCESS_TOKEN>` should be replaced with the OAuth 2 access token.

The uploaded file path in Dropbox is defined by the "path" parameter in Dropbox-API-Arg.

So, for example, to upload a file "test_php_upload.txt" to root, the path parameter should be "/test_php_upload.txt".

Here's a version of my previous example that would do that:

    <?php

    $path = 'test_php_upload.txt';
    $fp = fopen($path, 'rb');
    $size = filesize($path);

    $cheaders = array('Authorization: Bearer <ACCESS_TOKEN>',
                      'Content-Type: application/octet-stream',
                      'Dropbox-API-Arg: {"path":"/'.$path.'", "mode":"add"}');

    $ch = curl_init('https://content.dropboxapi.com/2/files/upload');
    curl_setopt($ch, CURLOPT_HTTPHEADER, $cheaders);
    curl_setopt($ch, CURLOPT_PUT, true);
    curl_setopt($ch, CURLOPT_CUSTOMREQUEST, 'POST');
    curl_setopt($ch, CURLOPT_INFILE, $fp);
    curl_setopt($ch, CURLOPT_INFILESIZE, $size);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    $response = curl_exec($ch);

    echo $response;
    curl_close($ch);
    fclose($fp);

    ?>