PHP Array Issue when using as parameter

1. PHP function passes arguments with copying

--> you can use &

ex)
function addSomeValueIntoArray(&$targetArray, $value)

2. Order of array_push when using nested array

ex)
<BAD>
$parentArray = array();
$childArray = ["foo" => bar];
array_push($parentArray, $childArray);
//Not reflected in parentArray
array_push($childArray, ["hello" => "world"]);

<Correct>
$parentArray = array();
$childArray = ["foo" => bar];
array_push($childArray, ["hello" => "world"]);
array_push($parentArray, $childArray);