Converts all img src URLs to base64 data urls. Very crude, doesn't check the MIME type, probably som regex issues to.

URLtoData

function URLtoData($html) {
    $imgTags = null;
    preg_match_all("/<img.*?>/", $html, $imgTags);

    foreach ($imgTags[0] as $imgTag) {
        $src = null;
        preg_match_all("/src=\"([^\"]*)/", $imgTag, $src);
        $src = $src[1][0];

        $data = base64_encode(file_get_contents($src));
        $html = str_replace($src, "data:image/jpg;base64,{$data}", $html);
    }

    return $html;
}