Merge two arrays and retain only unique values.
Append values from second array.
Do not care about keys.
<?php
$array1 = [
0 => 'apple',
1 => 'orange',
2 => 'pear',
];
$array2 = [
0 => 'melon',
1 => 'orange',
2 => 'banana',
];
$result = array_keys(
array_flip($array1) + array_flip($array2)
);
?>
Result:
[
[0] => "apple",
[1] => "orange",
[2] => "pear",
[3] => "melon",
[4] => "banana",
}