+/**
+ * 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.
+ //
+ // Note: empty regex //u also caused NULL return on some
+ // production machines, but none of our test machines.
+ //
+ // This should be replaced with a more reliable check.
+ return preg_replace('/\x00/u', '', $str);
+}
+
+/**
+ * Make sure an arbitrary string is safe for output in XML as a single line.
+ *
+ * @param string $str
+ * @return string
+ */