<?php
$data = [
    'foo',
    'baz' => 'Baz',
    'bar',
];

var_dump($data);

/*
array(3) {
  [0]=>
  string(3) "foo"
  ["baz"]=>
  string(3) "Baz"
  [1]=>
  string(3) "bar"
}
*/