php array union http://php.net/manual/en/language.operators.array.php

index.php

<?php

// php array union
// http://php.net/manual/en/language.operators.array.php

$foo = [
    'bar',
    'baz',
    'qux',
];
    
$fuzz = [0 => 'buzz'] + $foo;

var_dump($fuzz);

/*
array(3) {
  [0]=>
  string(4) "buzz"
  [1]=>
  string(3) "baz"
  [2]=>
  string(3) "qux"
}
*/