esc_xml( string $text ): string

4760function esc_xml( $text ) {4761	$safe_text = wp_check_invalid_utf8( $text );4762 4763	$cdata_regex = '\<\!\[CDATA\[.*?\]\]\>';4764	$regex       = <<<EOF4765/4766	(?=.*?{$cdata_regex})                 # lookahead that will match anything followed by a CDATA Section4767	(?<non_cdata_followed_by_cdata>(.*?)) # the "anything" matched by the lookahead4768	(?<cdata>({$cdata_regex}))            # the CDATA Section matched by the lookahead4769 4770|	                                      # alternative4771 4772	(?<non_cdata>(.*))                    # non-CDATA Section4773/sx4774EOF;4775 4776	$safe_text = (string) preg_replace_callback(4777		$regex,4778		static function ( $matches ) {4779			if ( ! isset( $matches[0] ) ) {4780				return '';4781			}4782 4783			if ( isset( $matches['non_cdata'] ) ) {4784				// escape HTML entities in the non-CDATA Section.4785				return _wp_specialchars( $matches['non_cdata'], ENT_XML1 );4786			}4787 4788			// Return the CDATA Section unchanged, escape HTML entities in the rest.4789			return _wp_specialchars( $matches['non_cdata_followed_by_cdata'], ENT_XML1 ) . $matches['cdata'];4790		},4791		$safe_text4792	);4793 4794	/**4795	 * Filters a string cleaned and escaped for output in XML.4796	 *4797	 * Text passed to esc_xml() is stripped of invalid or special characters4798	 * before output. HTML named character references are converted to their4799	 * equivalent code points.4800	 *4801	 * @since 5.5.04802	 *4803	 * @param string $safe_text The text after it has been escaped.4804	 * @param string $text      The text prior to being escaped.4805	 */4806	return apply_filters( 'esc_xml', $safe_text, $text );4807}
When	Instructions	Calls it makes
`!isset($matches)`	4	none
`isset($matches)`	12–14	`_wp_specialchars()`