[rchaud]

An expert wouldn't go to W3schools to begin with. They would have far more specific problems that would be better explored on Stack Overflow.

A beginner on the other hand would have their SO questions locked/closed within minutes because it would likely break any one of the thousand little rules SO has (to reduce duplicates) that are unknown to beginners.

Horses for courses; I read the official MDN and PHP docs now, but I didn't when I began because those sites assume an enormous amount of prior knowledge about programming.

[account-5]

This exactly. I still look to w3school over mdn if I can. The information is just friendlier. I'll use "proper" documentation if needed and never post anything to SO for the reasons you state.