public static function isSignValid( $given_sign , $values , $username = null ) {
		return ( self::sign( $values , $username ) === $given_sign );
	}
public static function isSignValid( $given_sign , $values , $username = null ) {
		return ( self::sign( $values , $username ) === $given_sign );
	}
public static function isSignValid ( $ given_sign , $ values , $ username = null ) { return ( self :: sign ( $ values , $ username ) === $ given_sign ) ; }
Tell whether a signature is valid for given values or not

@param   string   $given_sign  the provided signature
@param   array    $values      an array of values to certify
@param   string   $username    the user who has signed values or null for an instance signature

@return  boolean               ok or not
Tell whether a signature is valid for given values or not