using function (preg_match)

$f = fopen("http://gamethu.vnexpress.net/News/Dang-choi/", "rb"); // url using
$contents = '';

while (!feof($f)) {

$contents .= fread($f,1000);

}

fclose($f);

$mau = '//si';

if(preg_match($mau,$contents,$str))

{  $xuat =("".$str[0]."");

echo ($xuat);

}

else{

echo("loi");

}