Open External Links in a New Tab

add_filter( 'the_content', function ( $content ) {

	// This snippet requires the DOMDocument class to be available.

	if ( ! class_exists( 'DOMDocument' ) ) {

		return $content;

	}

	if ( !is_single() || !in_the_loop() || !is_main_query() ) {

		return $content;

	}

	$dom          = new DOMDocument();

	$load_content = mb_convert_encoding( $content, 'HTML-ENTITIES', 'UTF-8' );

	if ( empty( $load_content ) ) {

		return $content;

	}

	@$dom->loadHTML( $load_content );

	$links = $dom->getElementsByTagName( 'a' );

	foreach ( $links as $link ) {

		if ( strpos( $link->getAttribute( 'href' ), home_url() ) !== false ) {

			continue;

		}

		$old_link = $link->C14N();

		$link->setAttribute( 'target', '_blank' );

		$link->setAttribute( 'rel', 'noopener noreferrer' );

		$content = str_replace( $old_link, $link->C14N(), $content );

	}

	return $content;

} );