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<?php $data = [ 2 => [ 3, ], 3 => [ 8, ], 4 => [ 5, ], 5 => [ 8, ], 6 => [ 3, 8, ], 7 => [ 2, 5, ], 8 => [ 3, 8, ], ]; $occurrences = []; $mapped = array_map(function (array $values) use (&$occurrences) { $index = serialize($values); if (!array_key_exists($index, $occurrences)) { $occurrences[$index] = 1; return 0; } $occurrences[$index]++; return $occurrences[$index] - 1; }, $data); var_dump($mapped);
Output for git.master, git.master_jit, rfc.property-hooks
array(7) { [2]=> int(0) [3]=> int(0) [4]=> int(0) [5]=> int(1) [6]=> int(0) [7]=> int(0) [8]=> int(1) }

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