Online PHP editor | output for Dc1pV

<?php $officialGrid = [ ['grid' => TRUE, 'time' => '08:00', 'content' => NULL], ['grid' => TRUE, 'time' => '09:00', 'content' => NULL] ]; $bookings = [ ['grid' => NULL, 'time' => '08:00', 'content' => 'Paul Simon'], ['grid' => NULL, 'time' => '08:00', 'content' => 'Art Garfunkel'], ['grid' => NULL, 'time' => '08:39', 'content' => 'Homer J. Simpson'] ]; $result = array_column($officialGrid, null, 'time'); foreach ($bookings as $row) { if (!isset($result[$row['time']])) { $result[$row['time']] = $row; } else { $result[$row['time']]['content'] = sprintf( '%s%s', (isset($result[$row['time']]['content']) ? "{$result[$row['time']]['content']}, " : ''), $row['content'] ); } } ksort($result); var_export(array_values($result));