How to force an HTML link to be absolute?

Question

In my website, users can put an URL in their profile.

This URL can be http://www.google.com or www.google.com or google.com.

If I just insert in my PHP code <a href="$url">$url</a>, the link is not always absolute.

How can I force the a tag to be absolute ?

Answer 1

If you prefix the URL with // it will be treated as an absolute one. For example:

<a href="//google.com">Google</a>.

Keep in mind this will use the same protocol the page is being served with (e.g. if your page's URL is https://path/to/page the resulting URL will be https://google.com).

Answer 2

I recently had to do something similar.

if (strpos($url, 'http') === false) {
    $url = 'http://' .$url;
}

Basically, if the url doesn't contain 'http' add it to the front of the string (prefix).

Or we can do this with RegEx

$http_pattern = "/^http[s]*:\/\/[\w]+/i";

if (!preg_match($http_pattern, $url, $match)){  
   $url = 'http://' .$url;
}  

Thank you to @JamesHilton for pointing out a mistake. Thank you!

Answer 3

Use a protocol, preferably http://

<a href="http://www.google.com">Google</a>

Ask users to enter url in this format, or concatenate http:// if not added.

If you prefix the URL only with //, it will use the same protocol the page is being served with.

<a href="//google.com">Google</a>