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<?php $a=array(); $a[1]=array('id'=>1,'name'=>'a1', 'elements'=>array()); $a[1]['elements'][2] = array('id'=>2,'name'=>'a2','elements'=>array()); print_r($a);
Output for 4.3.0 - 7.1.0
Array ( [1] => Array ( [id] => 1 [name] => a1 [elements] => Array ( [2] => Array ( [id] => 2 [name] => a2 [elements] => Array ( ) ) ) ) )