PHP - add item to beginning of associative array [duplicate]

Question

How can I add an item to the beginning of an associative array? For example, say I have an array like this:

$arr = array('key1' => 'value1', 'key2' => 'value2');

When I add something to it as in $arr['key0'] = 'value0';, I get:

Array
(
    [key1] => value1
    [key2] => value2
    [key0] => value0
)

How do I make that to be

Array
(
    [key0] => value0
    [key1] => value1
    [key2] => value2
)

Thanks,
Tee

Answer 1

You could use the union operator:

$arr1 = array('key0' => 'value0') + $arr1;

or array_merge.

Answer 2

One way is with array_merge:

<?php
$arr = array('key1' => 'value1', 'key2' => 'value2');
$arr = array_merge(array('key0' => 'value0'), $arr);

Depending on circumstances, you may also make use of ksort.

Answer 3

$array = array('key1' => 'value1', 'key2' => 'value2');
array_combine(array_unshift(array_keys($array),'key0'),array_unshift(array_values($array),'value0'))

Answer 4

function unshift( array & $array, $key, $val)
{
    $array = array_reverse($array, 1);
    $array[$key] = $val;
    $array = array_reverse($array, 1);

    return $array;
}

Answer 5

If you don't want to merge the arrays you could just use ksort() on the array before iterating over it.