$sql = “SELECT a.*, b.* from table1 a, table2 b WHERE a.id=b.id”; // example sql
$r = mysql_query($sql,$conn);
if (!$r) die(mysql_error());
$numfields = mysql_num_fields($r);
$tfields = Array();
for ($i=0;$i<$numfields;$i++)
{
    $field =  mysql_fetch_field($r,$i);
    $tfields[$i] = $field->table.’.’.$field->name;
}
while ($row = mysql_fetch_row($r))
{
    $rowAssoc = Array();
    for ($i=0;$i<$numfields;$i++)
    {
        $rowAssoc[$tfields[$i]] = $row[$i];
    }
//    do stuff with $rowAssoc as if it was $rowAssoc = mysql_fetch_assoc($r) you had used, but with table. prefixes
}