当table1.id = table2.id时如何打印一件事，而如果“ if else”又如何打印？

Question

I have a menu where some pages have sub-pages which open the drop-down menu.

I have two SQL tables:

'pages' => page_id, page_name; 'subpages' => subpage_id, page_id, page_name;

Subpages get same page_id as the chosen parent page has, when I insert them via my form.

The problem is, all menu elements show the drop-down arrow - even the ones without sub-pages.

How can I print something only if the page has sub-pages? This is what i want:

if pages.page_id=subpages.page_id  
print 
  <button class="dropdown-btn">
    <?php echo $page['page_name']; ?>
    <i class="fa fa-caret-down"></i>
  </button>

else print 
  <a href="#"><?php echo $page['page_name']; ?></a>

index.php:

<?php foreach ($pages as $page) { ?>

    <button class="dropdown-btn">
      <?php echo $page['page_name']; ?>
      <i class="fa fa-caret-down"></i>
    </button>

    <div class="dropdown-container">
<?php foreach ($subpages as $subpage) { 
  if($subpage['page_id'] == $page['page_id']) {
?>
  <a href="../subpage.php?id=<?php echo $subpage['subpage_id']; ?>">
    <?php echo $subpage['subpage_name']; ?>
  </a>
<?php } } ?>
    </div>

<?php } ?>

Any help is appreciated!

Answer 1

First of all I would change Subpage class like this:

class Subpage {
    public function fetch_all(){
        global $pdo;

        $query = $pdo->prepare("SELECT * FROM subpages");
        $query->execute();

        return $query->fetchAll();
    }

    // Static function: Fetch all subpages of single page
    public static function fetch_all_page($page_id){
        global $pdo;

        $query = $pdo->prepare("SELECT * FROM subpages WHERE page_id = ?");
        $query->bindValue(1, $page_id);
        $query->execute();

        return $query->fetchAll();
    }

    public function fetch_data($subpage_id) {
        global $pdo;

        $query = $pdo->prepare("SELECT * FROM subpages WHERE subpage_id =         
?");
        $query->bindValue(1, $subpage_id);
        $query->execute();

        return $query->fetch();
    }
} 

And your index.php will become:

<?php foreach ($pages as $page) { ?>

    <?php $subpages = Subpage::fetch_all_page($page['page_id']); ?>

    <button class="dropdown-btn">
        <?php echo $page['page_name']; ?>
        <?php if (count($subpages)): ?>
            <i class="fa fa-caret-down"></i>
        <?php endif; ?>
    </button>

    <div class="dropdown-container">
        <?php foreach ($subpages as $subpage): ?>
            <a href="../subpage.php?id=<?php echo $subpage['subpage_id']; ?>">
                <?php echo $subpage['subpage_name']; ?>
            </a>
        <?php endforeach; ?>
    </div>

<?php } ?>