Absolute URL's acting like relative URL's

问题

When I have a link like http://site.com, clicking it goes to that URL just fine.

But when the link is just www.site.com, it adds this URL to the parent website and consequently does not go to the URL.

So, clicking on <a href='www.site.com'>site</a> creates this in the browser taskbar: www.parentsite.com/www.site.com.

How can I fix this without using preg_replace? I am fairly new to this game.

回答1:

Because www.parentsite.com is interpreted as a relative address, like for example index.htm, as opposed to an absolute URL which consists of protocol, hostname, and path.

When I'm on example.com's front page....

• contact.html is a relative address, the absolute end result will be http://example.com/contact.html (the browser does this as an internal calculation)

• images/ is a relative address, resulting in http://example.com/images/

• www.xyz.com results in http://example.com/www.xyz.com

You need to prefix the protocol (eg. http://) to make the browser understand that you mean a full URL, and treat it accordingly.

Here's a background info article on the issue on MSDN.

来源：https://stackoverflow.com/questions/13276021/absolute-urls-acting-like-relative-urls