PHP array_merge with numerical keys

Question

How can make it so array_merge() overwrites two keys with different values but same key index from two arrays?

for example, merging:

[0] => 'whatever'

with

[0] => 'whatever', [1] => 'a', [2] => 'b'

should produce

[0] => 'whatever', [1] => 'a', [2] => 'b'

Basically I want array_merge to bahave the same way it behaves if the arrays have string keys...

Answer 1

the solution could be this:
function array_merge_custom($array1, $array2) {
    $mergeArray = [];
    $array1Keys = array_keys($array1);
    $array2Keys = array_keys($array2);
    $keys = array_merge($array1Keys, $array2Keys);

    foreach ($keys as $key) {
        $mergeArray[$key] = array_merge_recursive(isset($array1[$key]) ? $array1[$key] : [], isset($array2[$key]) ? $array2[$key] : []);
    }

    return $mergeArray;
}

$array1 = [
    '66_' => [
        'k1' => 1,
        'k2' => 1,
    ],
    '67_' => [
        'k1' => 1,
        'k2' => 1,
    ],
    '68_' => [
        'k1' => 1,
        'k2' => 1,
    ],
    68 => [
        'k1' => 1,
        'k2' => 1,
    ]
];
$array2 = [
    '66_' => [
        'a1' => 1,
        'a2' => 1,
    ],
    '68_' => [
        'b1' => 1,
        'b2' => 1,
    ],
    68 => [
        'b1' => 1,
        'b2' => 1,
    ]
];
echo '<pre>';
print_r(array_merge_custom($array1, $array2));

Answer 2

You should use $a2+$a1 to get same result with array_merge($a1,$a2);

$a1 = array(
    'k1' => 1,
    'k2' => 2,
    'k3' => 3,
);

$a2 = array(
    'k1' => 11,
    'k2' => 22,
    'k4' => 44,
);

Code:

print_r(array_merge($a1,$a2));

Output:

Array ( 
    [k1] => 11 
    [k2] => 22 
    [k3] => 3 
    [k4] => 44 
)

Code:

print_r($a1+$a2);

Output:

Array ( 
    [k1] => 1 
    [k2] => 2 
    [k3] => 3 
    [k4] => 44 
)

Code:

print_r($a2+$a1);

Output:

Array ( 
    [k1] => 11 
    [k2] => 22 
    [k4] => 44 
    [k3] => 3 
)