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<?php $arr = [ (object) [ "book" => "book 1", "n_ano" => "2013", ], (object) [ "book" => "book 2", "n_ano" => "2012", ], (object) [ "book" => "book 3", "n_ano" => "2013", ], ]; foreach($arr as $v) $data[$v->n_ano][] = $v->book; foreach($data as $n_ano => $books) { echo $n_ano . "<br>"; foreach($books as $book) echo " - " . $book . "<br>"; }
Output for 5.4.0 - 5.4.45, 5.5.0 - 5.5.38, 5.6.0 - 5.6.40, 7.0.0 - 7.0.33, 7.1.0 - 7.1.33, 7.2.0 - 7.2.33, 7.3.0 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.29, 8.2.0 - 8.2.20, 8.3.0 - 8.3.8
2013<br> - book 1<br> - book 3<br>2012<br> - book 2<br>
Output for 4.4.2 - 4.4.9, 5.1.0 - 5.1.6, 5.2.0 - 5.2.17, 5.3.0 - 5.3.29
Parse error: syntax error, unexpected '[' in /in/hl0qf on line 3
Process exited with code 255.
Output for 4.3.0 - 4.3.1, 4.3.5 - 4.3.11, 4.4.0 - 4.4.1, 5.0.0 - 5.0.5
Parse error: parse error, unexpected '[' in /in/hl0qf on line 3
Process exited with code 255.
Output for 4.3.2 - 4.3.4
Parse error: parse error in /in/hl0qf on line 3
Process exited with code 255.

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173.03 ms | 402 KiB | 464 Q