How do I check for valid (not dead) links programmatically using PHP?

Question

Given a list of urls, I would like to check that each url:

• Returns a 200 OK status code
• Returns a response within X amount of time

The

Answer 1

Just returning a 200 response is not enough; many valid links will continue to return "200" after they change into porn / gambling portals when the former owner fails to renew.

Domain squatters typically ensure that every URL in their domains returns 200.