Where are you (or more appropriately, the plant) located? Is it blooming now?

I'm in Jamaica W.I.
Yes it is blooming now.

It is a Hypericum spp. Possibly Hypericum ellipticum?

I'm not convinced it's a Hypericum.

It does look like the Talinum caffrum, but the plants we have do not grow from big trunks like I see in the photos of Talinum caffrum on the Internet. The flower is also slightly different.

When I burst open the ripen fruit of this yellow flowering plant/weed, these are the seeds that it has.

As I research more on the suggestion by floral_uk z.8/9 SW UK regarding Talinum plants, I've discovered that this plant may be the Talinum fruticosum (T. triangulare). Although all the pictures I've seen show that the Talinum fruticosum has purple flowers, this species can also have yellow, pink, red, or white flowers.

So I believe this plant is indeed the Talinum fruticosum (T. triangulare). It is actually eaten as a vegetable in some countries, maybe one day I'll nibble on one of its leaves. Thanks very much.

Same... We have both pink and yellow, haven't sampled yet

Always be certain of identification before eating a plant.