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run code in 300+ PHP versions simultaneously
<?php $array = array ( 0 => array ( 'company' => 1, 'product' => 5, ), 1 => array ( 'company' => 2, 'product' => 4, ), 2 => array ( 'company' => 6, 'product' => 5, ), 3 => array ( 'company' => 2, 'product' => 3, ), ); foreach ($array as $set) { if (!isset($result[$set['product']])) { $result[$set['product']] = $set; } else { $result[$set['product']]['company'] .= ",{$set['company']}"; } } var_export(array_values($result));

preferences:
24.06 ms | 405 KiB | 5 Q