I have this foreach loop:
foreach($aMbs as $aMemb){
$ignoreArray = array(1,3);
if (!in_array($aMemb[\'ID\'],$ignoreArray)){
$aMemberships[]
it prints an array of arrays because you are doing so in this line
$aMemberships[] = array($aMemb['ID'] => $aMemb['Name']);
where you [] after a variable your are indicating to assign the value in a new row of the array and you are inserting an other array into that row
so you can use the the examples the others haver already gave or you can use this method:
int array_push ( array &$array , mixed $var [, mixed $... ] )
here is an example that you can find in the api
"orange",1=>"banana");
array_push($stack, 2=>"apple",3=>"raspberry");
print_r($stack);
?>
//prints
Array
(
[0] => orange
[1] => banana
[2] => apple
[3] => raspberry
)
http://php.net/manual/en/function.array-push.php