# Strip Unicode bidi override characters.
		# Sometimes they slip into cut-n-pasted page titles, where the
		# override chars get included in list displays.
		$dbkey = preg_replace( '/\xE2\x80[\x8E\x8F\xAA-\xAE]/S', '', $dbkey );

		# Clean up whitespace
		# Note: use of the /u option on preg_replace here will cause
		# input with invalid UTF-8 sequences to be nullified out in PHP 5.2.x,
		# conveniently disabling them.
		$dbkey = preg_replace(
			'/[ _\xA0\x{1680}\x{180E}\x{2000}-\x{200A}\x{2028}\x{2029}\x{202F}\x{205F}\x{3000}]+/u',
			'_',
			$dbkey
		);
		$dbkey = trim( $dbkey, '_' );

		title = title
			// Normalise whitespace to underscores and remove duplicates
			.replace( /[ _\s]+/g, '_' )
			// Trim underscores
			.replace( rUnderscoreTrim, '' );