Associated array,insert element

PHP
1

I have an php array and I want to insert an element with the index -1 and value “none”.Bassicaly I use this code from cakephp

$customers = $this->Machine->customer->find
             (
    'list',
   array
   (
   'fields' => array('CUSTOMER_ID', 'CUSTOMER_NAME'),
    'order' => 'CUSTOMER_NAME ASC',
    'recursive' => -1
     )
             );

I used the array_push() but it did not work as I wanted

2

$array[-1]=“none”;