$json =
    '{"content" : "'.addslashes(chunk_split(base64_encode($file_contents))).'"}'

// create the object
$obj = array(
    "content" => chunk_split(base64_encode($file_contents))
);
// encode the object in JSON format
$json = json_encode($obj);

"image" :"${new BASE64Encoder().encode(data).replaceAll("[nr]", "")}"

// create the object
$obj = array(
    "content" => base64_encode($file_contents)
);
// encode the object in JSON format
$json = json_encode($obj);