Change Drupal DB table prefixes in a dirty way using Page with PHP filter

change_db_prefix.php

<form action="" method="get">
Old prefix: <input type="text" name="old" /> <br />
New prefix: <input type="text" name="new" /> <br />
<input type="submit" value="Rename" />
</form>
<?php

global $db_prefix;

if ($old = $_REQUEST['old'] || $new = $_REQUEST['new']) {
  $result = db_query("SHOW TABLES");
  while ($r = db_fetch_array($result)) {
   $table_old = current($r);
   $table_new = $new.str_replace('^'.$old, '', $table_old);
   db_query("RENAME TABLE {$table_old} TO {$table_new}");
   print "{$table_old} &mdash;&gt; {$table_new} <br />";
  }

  $db_prefix = $new;
}