Function array_merge exists since PHP 4:

<?php
$data = [1, 3, 4];

$values = [5, 6];

$data = array_merge($values, $data);

print_r($data);

Live PHP sandbox

The API of ArrayObject does not have any function to accomplish this directly. You have several other options:

• Manually move each element by 1, and set your new value at index 0 (only if you have a numerically index ArrayObject).

 $tmp = NULL;
 for ($i = 0; $arrayObject->offsetExists($i + 1); $i++) {
      $tmp = $arrayObject->offsetGet($i + 1);
      $arrayObject->offsetSet($i + 1, $arrayObject->offsetGet($i));
 }
 $arrayObject->offsetSet($i, $tmp);
 $arrayObject->offsetSet(0, $new_value);

• Write a class deriving from ArrayObject and add a function prepend (implementation could be the one below).
• Extract an array, call array_unshift() and create a new ArrayObject with the modified array:

 $array = $arrayObject->getArrayCopy();
 array_unshift($array, $new_value);
 $arrayObject->exchangeArray($array);

Use array_unshift($array, $item);

$arr = array('item2', 'item3', 'item4');
array_unshift($arr , 'item1');
print_r($arr);

will give you

Array
(
 [0] => item1
 [1] => item2
 [2] => item3
 [3] => item4
)

You could use

array_merge()

For example

$resultingArray = array_merge(array($newElement), $originalArray);