Put multiple querys in array

How would I go on to do these mysql_querys

mysql_query("SELECT * FROM my_table_1");
mysql_query("SELECT * FROM my_table_2");
mysql_query("SELECT * FROM my_table_3");
mysql_query("SELECT * FROM my_table_4");

..and put all the results in a array and echo that array..?

 

$tables = array('my_table_1', 'my_table_2', 'my_table_3', 'my_table_4');
$result_array = array();
foreach ($tables as $table)
{
   $sql = "select * from {$table}";
   $st = mysql_query($sql) or die (mysql_error());
   while ($row = mysql_fetch_row($st))
      $result_array[] = $row;
}
echo "<table border='1'>";
foreach ($result_array as $row)
   echo "<tr><td>" . join("</td><td>", $row) . "</td></tr>";
echo "</table>";

PHP:

 

If the tables are large, running scripts like this use up a lot of memory. It also increases overhead and execution time by a lot.

I would look into using UNION
http://dev.mysql.com/doc/refman/5.0/en/union.html

 

If the tables are large, using UNION will take up more RAM because the result set will be larger. Although I could have used a mysql_free_result() in the loop...

The original request seems a bit wonky to me, in almost 15 years of using PHP I've never seen a reason to do that.