Quiero

Here is link: http://google.com
And http://example.com inside.
And another one at the very end: http://test.net

convertirse

Here is link: <a href="http://google.com">http://google.com</a>
And <a href="http://example.com">http://example.com</a> inside.
And another one at the very end: <a href="http://test.net">http://test.net</a>

Parece una tarea trivial, pero no puedo encontrar una función PHP que funcione. ¿Tienes alguna idea

function make_links_clickable($text){
    // ???
}

$text = 'Here is link: http://google.com
And http://example.com inside.
And another one at the very end: http://test.net';

echo make_links_clickable($text);