CREATE DATABASE IF NOT EXISTS 'drupal_mydatabase';
USE 'drupal_mydatabase';

<?php
$db_server = "localhost";    // hostname MySQL server
$db_username = "username";   // username MySQL server
$db_password = "password";   // password MySQL server
$db_name = "database";       // database name

$pattern = "pattern_";          // search string for example: "drpl_"
$new_pattern = "new_pattern_";  // replacement string.
                            // can be empty. For example "" for no db prefix

// login to MySQL server
$link = mysql_connect( $db_server, $db_username, $db_password);

if (!$link)
{
  die('Could not connect: ' . mysql_error());
}

// list all tables in the database containing the search pattern
$sql = "SHOW TABLES FROM `" . $db_name . "`";
$sql .= " LIKE '%" . $pattern . "%'";

$result = mysql_query ( $sql, $link );
if (!$result)
{
  die("Invalid query: " . mysql_error( $link ));
}

$renamed = 0;
$failed = 0;

while ( $row = mysql_fetch_array ($result) )
{
  // rename every table by replacing the search pattern
  // with a new pattern
  $table_name = $row[0];
  $new_table_name = str_replace ( $pattern, $new_pattern, $table_name);

  $sql = "RENAME TABLE `" . $db_name . "`.`" . $table_name . "`";
  $sql .= " TO `" . $db_name . "`.`" . $new_table_name . "`";

  $result_rename = mysql_query ( $sql, $link );
  if ($result_rename)
  {
    echo "Table `" . $table_name . "` renamed to :`";
    echo $new_table_name . "`.n";
    $renamed++;
  }
  else
  {
    // notify when the renaming failed and show reason why
    echo "Renaming of table `" . $table_name . "` has failed: ";
    echo mysql_error( $link ) . "n";
    $failed++;
  }
}

echo $renamed . " tables were renamed, " . $failed . " failed.n";

// close connection to MySQL server
mysql_close( $link );
?>

array (
  'database' => 'sample_drupal_db',
  'username' => 'sample_drupal_usr',
  'password' => 'sample_drupal_pwd',
  'host' => 'localhost',
  'port' => '',
  'driver' => 'mysql',
  'prefix' => 'prefix_', // <<== prefix here
),