Issue #307 Update README

mikehaertl · mikehaertl · commit 96c78ad43621 · 2019-03-12T08:03:18.000+01:00
diff --git a/README.md b/README.md
@@ -188,6 +188,23 @@ $pdf = new Pdf(array(
 ));
 ```
 
+### Passing strings
+
+Some options like `header-html` usually expect a URL or a filename. With our
+library you can also pass a string. The class will try to detect if the
+argument is a URL, a filename or some HTML or XML content.  To make detection
+easier you can surround your content in `<html>` tag.
+
+If this doesn't work correctly you can also pass an instance of our `File`
+helper as a last resort:
+
+```php
+use mikehaertl\tmp\File;
+$options = [
+    'header-html' => new File('Complex content', '.html'),
+];
+```
+
 ## Error handling
 
 `send()`, `saveAs()` and `toString()` will return `false` on error. In this case the detailed error message is
