PHP prepend associative array with literal keys?

You cannot directly prepend an associative array with a key-value pair.

However, you can create a new array that contains the new key-value pair at the beginning of the array with the union operator +. The outcome is an entirely new array though and creating the new array has O(n) complexity.

The syntax is below.

$new_array = array('new_key' => 'value') + $original_array;

Note: Do not use array_merge(). array_merge() overwrites keys and does not preserve numeric keys.

Can't you just do:

$resulting_array = $array2 + $array1;

?