_canonical_charset()

_canonical_charset( string $charset ): string

function _canonical_charset( $charset ) {
	if ( is_utf8_charset( $charset ) ) {
		return 'UTF-8';
	}

	/*
	 * Normalize the ISO-8859-1 family of languages.
	 *
	 * This is not required for htmlspecialchars(), as it properly recognizes all of
	 * the input character sets that here are transformed into "ISO-8859-1".
	 *
	 * @todo Should this entire check be removed since it's not required for the stated purpose?
	 * @todo Should WordPress transform other potential charset equivalents, such as "latin1"?
	 */
	if (
		( 0 === strcasecmp( 'iso-8859-1', $charset ) ) ||
		( 0 === strcasecmp( 'iso8859-1', $charset ) )
	) {
		return 'ISO-8859-1';
	}

	return $charset;
}