How to dump and compress all mysql databases on a server into separate files using PHP and PEAR

Here's a quick code snippet I just wrote to dump and compress (gzip) all mysql databases on a server into separate files using PHP and PEAR.

<?php

// include PEAR DB library
require_once('DB.php');

// define the DSN in an array
// NOTE: user must have access to all databases
$dsn = array(
  'phptype' => 'mysql',
  'username' => 'YOURUSER',
  'password' => 'YOURPASSWORD',
  'hostspec' => 'HOSTNAME', // localhost?
);

// instantiate a PEAR DB object
$DB =& DB::connect($dsn);

// check for an error
if (DB::isError($DB)) die($DB->getMessage());

// set the DB fetch mode to associative
$DB->setFetchMode(DB_FETCHMODE_ASSOC);

// define sql statement
$sql = "show databases";

// fetch sql result
$databases = $DB->getAll($sql);

// loop through results
foreach ($databases as $index => $result) {

  // define the mysqldump command
  $command = "mysqldump -u " . $dsn['username'] . " "
    . "-p" . $dsn['password'] . " "
    . "-h " . $dsn['hostspec'] . " "
    . $result['Database'] . " | gzip > "
    . $result['Database'] . ".sql.gz";

  // execute command
  `$command`;

}
?>