Associative Array Sum

<?php

$data = array(
  0 => array(
    'event' => 'Conference',
    'budget' => 3700,
  ),
  1 => array(
    'event' => 'Conference',
    'budget' => 500,
  ),
  2 => array(
    'event' => 'Showroom',
    'budget' => 1000,
  ),
  3 => array(
    'event' => 'Mission Chez client',
    'budget' => 2000,
  ),
  4 => array(
    'event' => 'Séminaire',
    'budget' => 700,
  ),
  5 => array(
    'event' => 'Livraison',
    'budget' => 4000,
  ),
  6 => array(
    'event' => 'Conference',
    'budget' => 334,
  ),
);

$sum = array_reduce($data, function ($a, $b) {
    isset($a[$b['event']]) ? $a[$b['event']]['budget'] += $b['budget'] : $a[$b['event']] = $b;  
    return $a;
});

print_r(array_values($sum));

?>