Do not require a PHP start tag for syntax highlighting

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

developer_manual/conf.py

@@ -316,3 +316,7 @@ StandaloneHTMLBuilder.supported_image_types = [
 # Generate the versions list
 html_context['versions'] = generateVersionsDocs(current_docs)
 html_context['theme_vcs_pageview_mode'] += current_docs
+
+highlight_options = {
+  'php': {'startinline': True},
+}