+
+/**
+ * Returns the regexp for common whitespace characters.
+ *
+ * By default, spaces include new lines, tabs, nbsp entities, and the UTF-8 nbsp.
+ * This is designed to replace the PCRE \s sequence. In ticket #22692, that
+ * sequence was found to be unreliable due to random inclusion of the A0 byte.
+ *
+ * @since 4.0.0
+ *
+ * @return string The spaces regexp.
+ */
+function wp_spaces_regexp() {
+ static $spaces;
+
+ if ( empty( $spaces ) ) {
+ /**
+ * Filter the regexp for common whitespace characters.
+ *
+ * This string is substituted for the \s sequence as needed in regular
+ * expressions. For websites not written in English, different characters
+ * may represent whitespace. For websites not encoded in UTF-8, the 0xC2 0xA0
+ * sequence may not be in use.
+ *
+ * @since 4.0.0
+ *
+ * @param string $spaces Regexp pattern for matching common whitespace characters.
+ */
+ $spaces = apply_filters( 'wp_spaces_regexp', '[\r\n\t ]|\xC2\xA0| ' );
+ }
+
+ return $spaces;
+}