$text = 'Lorem ipsum http://thesite.com dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor
incididunt https://www.thesite.com ut labore et dolore magna aliqua. Ut http://www.thesite.com enim ad minim veniam,';
$pattern = '!(https?://[^\s]+)!'; // refine this for better/more specific results
if (preg_match_all($pattern, $text, $matches)) {
list(, $links) = ($matches);
print_r($links);
}