Merging two arrays without changing key values php

Question

I have two arrays in php as shown in the code

<?php
$a=array('0'=>array('500'=>'1','502'=>'2'));
$b=array('0'=>array('503'=>'3','504'=>'5'));
print_r(array_merge($a[0],$b[0]));
?>

I need to merge two arrays. array_merge function successfully merged two of them but key value gets changed. I need the following output

  Array
    (
        [0]=>Array(
           [500] => 1
           [502] => 2
           [503] => 3
           [504] => 5
         )
    )

What function can I use in php so that the following output is obtained without changing key values?

Answer 1

From the documentation, Example #3:

If you want to append array elements from the second array to the first array while not overwriting the elements from the first array and not re-indexing, use the + array union operator:

<?php
$array1 = array(0 => 'zero_a', 2 => 'two_a', 3 => 'three_a');
$array2 = array(1 => 'one_b', 3 => 'three_b', 4 => 'four_b');
$result = $array1 + $array2;
var_dump($result);
?>

The keys from the first array will be preserved. If an array key exists in both arrays, then the element from the first array will be used and the matching key's element from the second array will be ignored.

array(5) {
  [0]=>
  string(6) "zero_a"
  [2]=>
  string(5) "two_a"
  [3]=>
  string(7) "three_a"
  [1]=>
  string(5) "one_b"
  [4]=>
  string(6) "four_b"
}

Therefore, try: $a[0] + $b[0]

Answer 2

$a=array('0'=>array('500'=>'1','502'=>'2'));
$b=array('0'=>array('503'=>'3','504'=>'5'));

$c = $a + $b; //$c will be a merged array

see the answer for this question