fisharebest/webtrees

<?php

declare(strict_types=1);

/**
 * @var string $x
 * @var string $y
 * @var string $z
 */

?>
<input type="text" name="<?= e($x) ?>" class="d-none" aria-label="field1" value="ok">
<input type="text" name="<?= e($y) ?>" class="d-none" aria-label="field2" value="<?= e($z) ?>">

<script>
    document.getElementsByName(<?= json_encode($x, JSON_THROW_ON_ERROR) ?>)[0].value = document.getElementsByName(<?= json_encode($y, JSON_THROW_ON_ERROR) ?>)[0].value;
</script>