+/**
+ * Very basic stripping of invalid UTF-8 input text.
+ *
+ * @param string $str
+ * @return mixed string or null if invalid input
+ *
+ * @todo ideally we should drop bad chars, and maybe do some of the checks
+ * from common_xml_safe_str. But we can't strip newlines, etc.
+ * @todo Unicode normalization might also be useful, but not needed now.
+ */
+function common_validate_utf8($str)
+{
+ // preg_replace will return NULL on invalid UTF-8 input.
+ return preg_replace('//u', '', $str);
+}
+
+/**
+ * Make sure an arbitrary string is safe for output in XML as a single line.
+ *
+ * @param string $str
+ * @return string
+ */