if ():
endif;

what is this grammar and how to find a manual? thank you

<div class="am-u-sm-9 am-u-end">
    <select name="category[parent_id]"
            data-am-selected="{searchBox: 1, btnSize: "sm"}">
        <option value="0"></option>
        <?php if (isset($list)): foreach ($list as $first): ?>
            <option value="<?= $first["category_id"] ?>">
                <?= $first["name"] ?></option>
        <?php endforeach; endif; ?>
    </select>
</div>