how to export a mysql data table search query into csv using php?

hear is query

```
if ($_REQUEST["startfrom"]<>'' and $_REQUEST["end"]<>'') {
    $sql = "SELECT ECRNo,SalesDate,TimeSold,AmountDue,OutletName,ProductCode,Category,MealType,SUM(Quantity) AS Quantity1,SUM(NetPrice) AS NetPrice1 FROM ".$SETTINGS["data_table"]." WHERE SalesDate BETWEEN '".mysql_real_escape_string($_REQUEST["startfrom"])."'And'".mysql_real_escape_string($_REQUEST["end"])."'".$search_OutletName.$search_Category.$search_ProductCode.$search_groupby;
} else if ($_REQUEST["startfrom"]<>'') {
    $sql = "SELECT ECRNo,SalesDate,TimeSold,AmountDue,SalesDate,OutletName,ProductCode,Category,MealType,SUM(Quantity) AS Quantity1,SUM(NetPrice) AS NetPrice1 FROM ".$SETTINGS["data_table"]." WHERE SalesDate >= '".mysql_real_escape_string($_REQUEST["startfrom"])."'".$search_OutletName.$search_Category.$search_ProductCode.$search_groupby;
} else if ($_REQUEST["end"]<>'') {
    $sql = "SELECT ECRNo,SalesDate,TimeSold,SalesDate,AmountDue,OutletName,ProductCode,Category,MealType,SUM(Quantity) AS Quantity1,SUM(NetPrice) AS NetPrice1 FROM ".$SETTINGS["data_table"]." WHERE SalesDate <= '".mysql_real_escape_string($_REQUEST["end"])."'".$search_OutletName.$search_Category.$search_ProductCode.$search_groupby;
}else {
    $sql = "SELECT ECRNo,SalesDate,TimeSold,SalesDate,AmountDue,OutletName,ProductCode,Category,MealType,SUM(Quantity) AS Quantity1,SUM(NetPrice) AS NetPrice1 FROM ".$SETTINGS["data_table"]." WHERE ECRNo>0 ".$search_OutletName.$search_Category.$search_ProductCode.$search_groupby;
}

```

how do i export its query result?