Flowers that came like a surprise

In July last year, I was temporarily staying at a duplex. In its small back yard, there were a couple of shallow rectangular clay dishes not being used, with some used potting mix in them. I decided to make use of them so I sowed some lettuce seeds.
After the lettuce grew to about four leaves big, I noticed that there were some sprouting activities which didn't look like normal weeds. They had thicker, fatter leaves in sets of 5 or so like a star. I pulled out some but then changed my mind. I wanted to wait and see what they grew to be like.
After a couple of months waiting, I was pretty sure they weren't weeds, but looked rather like some sort of annual plant.
Before long, they produced some little cup-shaped flowers that open for a bit over one day. They continue to produce buds every day, but each flower was short-lived. I was told the name of "portulaca", being a rock garden succulent. The flowers have many colours from white, pink to yellow and orange.