IC-Winner

function insertToArray($array=array(), $new=array(), $after='') {
  $res = array();
  $res1 = array();
  $res2 = array();
  $c = 0;
  $n = 0;
  foreach ($array as $k => $v) {
    if ($k == $after) { 
      $n = $c;
    } 
    $c++;
  }
  $c = 0;
  foreach ($array as $i => $a) {
    if ($c > $n) { 
      $res1[$i] = $a;
    } else {
      $res2[$i] = $a;
    }
    $c++;
  }
  $res = $res2 + $new + $res1;
  return $res;
}

$arr = array(
'key1' => 0,
'key2' => 0,
'keyN' => 0,
);

$new = array('new' => 0);
$arr = insertToArray($arr, $new, 'key2');

echo '<pre>'; print_r($arr); echo '</pre>';

Array
(
    [key1] => 0
    [key2] => 0
    [new] => 0
    [keyN] => 0
)