Diego your question is too wide, but to give you a basis.
How To Do This?
basically there are several classes ready PHP that facilitate and much this process, look on the internet for web scraping, web crawlers, spider bot
.
What do they do?
with these powerful classes you can call a function by passing the site and the id of the element that Voce wants to copy, for example:
$temperatura_atual = copiar_texto('www.google.com/site/previsao_tempo/sp/mooca/hoje', 'id_elemento_com_texto_da_provisao');
Easy, no? and now with this variable with the value, just save in the database. There is enough video on the internet.
Some libraries that do this kind of service:
https://stackoverflow.com/questions/4842371/what-php-web-crawler-libraries-are-available
Its north is: web scraping.
– Woss
Show. Thanks man!
– Diego Vieira