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<?php $myData = array( array('key2' => 'value1', 'key3' => 'value1', 'key4' => 'value4'), array('key4' => 'value4'), array('key1' => 'value1', 'key4' => 'value4'), array('key1' => 'value1', 'key2' => 'value1', 'key3' => 'value1', 'key4' => 'value4') ); usort($myData, function ($a, $b) { return count($b) - count($a); }); print_r($myData);
Output for 7.2.0 - 7.2.34, 7.3.0 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.33, 8.2.0 - 8.2.29, 8.3.0 - 8.3.25, 8.4.1 - 8.4.12
Array ( [0] => Array ( [key1] => value1 [key2] => value1 [key3] => value1 [key4] => value4 ) [1] => Array ( [key2] => value1 [key3] => value1 [key4] => value4 ) [2] => Array ( [key1] => value1 [key4] => value4 ) [3] => Array ( [key4] => value4 ) )

preferences:
146.13 ms | 408 KiB | 5 Q