Yes you can
<?php
$contents = file_get_contents("http://en.wikipedia.org/wiki/PHP");
preg_match("/<p>(.*?)<\/p>/", $contents, $match);
echo $match[1];
?>
http://sandbox.phpcode.eu/g/45c56.php
EDIT: Looks like they don't like non-validated browser agents. You'll have to do it with curl
EDIT2: curl with browser agent:
<?php
$ch = curl_init("http://en.wikipedia.org/wiki/PHP");
$useragent="Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.1) Gecko/20061204 Firefox/2.0.0.1";
curl_setopt($ch, CURLOPT_USERAGENT, $useragent);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$contents = curl_exec($ch);
preg_match("/<p>(.*?)<\/p>/", $contents, $match);
$match[1] = preg_replace("|\[[0-9]\]|", "", strip_tags($match[1]));
echo (($match[1]));
?>
http://sandbox.phpcode.eu/g/ad578.php