PDF格式的字符串中的奇怪符号但不包含在字符串中？

I am printing a string to a PDF. When I var_dump the string it looks pretty normal, no special chars or symbols are printed. After printing it to a PDF, it looks like this though:

https://screenshots.firefox.com/Fo1oucu7rCBnfdoc/null

As you can see, it prints something that looks like a closing button twice, sometimes once, but its always somewhere. Where it appears there is nothing visible in the string which could be replaced by this. This is the code I use for printing:

$text[] = $myText;
foreach ($text as $part) {
    $page->drawText(strip_tags(ltrim($part)), 285, $y - 50, 'UTF-8');
    $y -= 15;
}

If I fill $myText with just some static string, it works perfectly, no strange symbols are shown. Any ideas how to fix that?

Thanks!