Str@nnik,
$req = mysql_query("SELECT `id` FROM `champktp_players` WHERE `player_id` = '". $who ."';");
$temp = [];
while ($res = mysql_fetch_assoc($req)) {
$temp[] = $res['id'];
}
mysql_query("UPDATE `champktp_players` SET `player_id` = '". $who ."' WHERE `player_id` = '". $from ."';");
mysql_query("UPDATE `champktp_players` SET `player_id` = '". $from ."' WHERE `id` IN (". join($temp, ', ') .");");