php/WP_CLI/SynopsisParser.php
private static function is_optional( $token ) {
		if ( '[' === substr( $token, 0, 1 ) && ']' === substr( $token, -1 ) ) {
			return array( true, substr( $token, 1, -1 ) );
		}

		return array( false, $token );
	}
private static function is_optional( $token ) {
		if ( '[' === substr( $token, 0, 1 ) && ']' === substr( $token, -1 ) ) {
			return array( true, substr( $token, 1, -1 ) );
		}

		return array( false, $token );
	}
private static function is_optional ( $ token ) { if ( '[' === substr ( $ token , 0 , 1 ) && ']' === substr ( $ token , - 1 ) ) { return array ( true , substr ( $ token , 1 , - 1 ) ) ; } return array ( false , $ token ) ; }
An optional parameter is surrounded by square brackets.

@param string $token
@return array
An optional parameter is surrounded by square brackets .