Upgrading database query code to MYSQLi or PDO

Are there direct command replacements for the following, or is there more to it than that?

$st1 = "SELECT * from `members` WHERE (memberid ='$usernum')";
$r1 = mysql_query($st1, $sqlsession);

if (mysql_num_rows($r1) )
{
while ($r2= mysql_fetch_array($r1)) {
[whatever]
}
}

I know the above well, but new to MYSQLi or PDO

Thanks!

 

You're in the wrong forum - this has nothing to do with mysql, it does, however, have everything to do with PHP. I suggest you take your question there. I'm on my phone, elsewise I'd write a suggestion.