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<?php $array = [ [ 'key_1' => 'FOO', 'key_2' => 'FTU-1', 'cats' => '/30/' ], [ 'key_1' => 'FOO', 'key_2' => 'FTU-2', 'cats' => '/30/' ], [ 'key_1' => 'FOO', 'key_2' => 'FTU-3', 'cats' => '/30/10/' ], [ 'key_1' => 'FOO', 'key_2' => 'FTU-4', 'cats' => '/15/' ], [ 'key_1' => 'FOO', 'key_2' => 'FTU-5', 'cats' => '/10/' ], [ 'key_1' => 'FOO', 'key_2' => 'FTU-6', 'cats' => '/15/' ], ]; $result = []; foreach ($array as $row) { foreach (explode('/', trim($row['cats'], '/')) as $cat) { $result[$cat][] = $row; } } var_export($result);
Output for 8.1.0 - 8.1.34, 8.2.0 - 8.2.30, 8.3.0 - 8.3.30, 8.4.1 - 8.4.18, 8.5.0 - 8.5.3
array ( 30 => array ( 0 => array ( 'key_1' => 'FOO', 'key_2' => 'FTU-1', 'cats' => '/30/', ), 1 => array ( 'key_1' => 'FOO', 'key_2' => 'FTU-2', 'cats' => '/30/', ), 2 => array ( 'key_1' => 'FOO', 'key_2' => 'FTU-3', 'cats' => '/30/10/', ), ), 10 => array ( 0 => array ( 'key_1' => 'FOO', 'key_2' => 'FTU-3', 'cats' => '/30/10/', ), 1 => array ( 'key_1' => 'FOO', 'key_2' => 'FTU-5', 'cats' => '/10/', ), ), 15 => array ( 0 => array ( 'key_1' => 'FOO', 'key_2' => 'FTU-4', 'cats' => '/15/', ), 1 => array ( 'key_1' => 'FOO', 'key_2' => 'FTU-6', 'cats' => '/15/', ), ), )

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