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run code in 200+ php & hhvm versions
<?php $arr1 = array( 4 => 'a', 'k' => array( 4 => 'a' ) ); $arr2 = array( 5 => 'b', 'k' => array( 5 => 'b' ) ); $arr3 = array_merge_recursive( $arr1, $arr2 ); var_dump( $arr3 );
Output for 4.3.0 - 5.6.30, hhvm-3.10.1 - 3.22.0, 7.0.0 - 7.2.6
array(3) { [0]=> string(1) "a" ["k"]=> array(2) { [4]=> string(1) "a" [5]=> string(1) "b" } [1]=> string(1) "b" }