select columns in table from array list

Hi 

I have a task that a user provides a text file with a list of mysql column names from a table. I need to select and display the results from the selected columns. the column names vary each time they are provided. I have decided to load the column name list to an array and would like to use this to  echo out the columns. I have made an attempt at this below but I'm not sure how to make it work. 

Any help would be appreciated. 

//load patient list to array 

$file = fopen("upload/PatList.txt", "r");
$all_pats = array();
while (!feof($file)) {
   $all_pats[] = fgets($file);
   }
fclose($file);

//var_dump($all_pats);

}



// select columns from array elements
 $qry=mysql_query("SELECT *
FROM mytable", $con);

 while($row=mysql_fetch_array($qry))
 {
echo "<td>".@$row{$column_name}. "<br></td>";

}