PEAR2_MultiErrors provides a simple and effective mechanism for aggregating many errors and organizing them by severity.

Errors are represented by PHP's built in exception object, and
severity levels are represented by PHP's pre-defined error levels
E_ERROR, E_WARNING, or E_NOTICE.  Adding errors to the PEAR2_MultiErrors
object is simple, and done like adding to an array.  Retrieving errors can
be done with iteration, and count() can be used to determine whether errors
were added.

<?php
include '/path/to/PEAR2/Autoload.php';
$a = new PEAR2\MultiErrors;
$a->E_ERROR[] = new Exception('message one');
$a->E_WARNING[] = new PEAR2\Blah\Exception('message two');
// iterate over all errors
foreach ($a as $error) {...}
// iterate over E_ERROR severity
foreach ($a->E_ERROR as $error) {...}
count($a); // 2
count($a->E_ERROR); // 1
count($a->E_WARNING); // 1
count(E_NOTICE); // 0
?>

Used in conjuction with PEAR2\Exception, it can also be used as a "cause"
of an Exception:

<?php
include '/path/to/PEAR2/Autoload.php';
$a = new PEAR2\MultiErrors;
$a->E_ERROR[] = new Exception('message one');
$a->E_ERROR[] = new PEAR2\Blah\Exception('message two');
throw new PEAR2\My\Exception('task failed', $a);
?>