Hey can anyone tell me why input data wont save in my database?

[dontilydondon]

I'm new to php and I'm trying to make a create article page for my site and so far the user is not able to create one because the code is not inserting into the database.
i keep getting error messages that some variables are undefined for example:
Undefined variable $authors in C:\xampp\htdocs\create.article.php:198 and
Undefined variable $extension in C:\xampp\htdocs\create.article.php:253.
i provided some code here:
After the user inputs data into the text bars nothing happens and i get an error 500.

$article = [
    'id' => $id, 'title' => '',
    'summary' => '', 'content' => '',
    'member_id' => 0, 'category_id' => 0,
    'image_id' => null, 'published' => false,
    'image_file' => '', 'image_alt' => '',
];

$errors = [
 'warning' => '',
  'title' => '',
  'summary' => '',
  'content' => '',
  'author' => '',
  'category' => '',
  'image_file' => '',
  'image_alt' => '',
];

if ($id) {
$sql = "SELECT a.id, a.title, a.summary, a.content, 
a.category_id, a.member_id, a.image_id, a.published,
i.file      AS image_file,
i.alt       AS image_alt
FROM article     AS a
LEFT JOIN image  AS i ON a.image_id = i.id
WHERE a.id = :id;";

$article = pdo($pdo, $sql, [$id])->fetch();

if (!$article) {
redirect('create1.articlepage.php', ['Failure' => 'article not found']);
    }
}

$saved_image = $article['image_file'] ? true : false;

$sql = "SELECT id, forename, surname FROM member;";   
$authors = pdo($pdo, $sql)->fetchAll();

$sql = "SELECT id, name FROM category;";
$categories = pdo($pdo, $sql)->fetchAll();

if ($_SERVER['REQUEST_METHOD'] == 'POST') {

$errors['image_file'] = ($temp === '' and $_FILES['image']['error'] === 1) ? 'File to big ' : '';

if ($temp and $_FILES['image']['error'] === 0) {
$article['image_alt'] = $_POST['image_alt'];

$errors['image_file'] = in_array(mime_content_type($temp), $file_types) ? '' : 'Wrong file type. ';

$extension = strtolower(pathinfo($_FILES['image']['name'], PATHINFO_EXTENSION));

$errors['image_file'] .= in_array($extension, $file_extensions) ? '' : 'Wrong file extention ';

$errors['image_file'] .= ($_FILES['image']['size'] <= $max_size) ? '' : 'File size too big. ';

$errors['image_alt'] = (is_text($article['image_alt'], 1, 254)) ? '' : 'Alt text must be 1-254 characters. ';

if ($errors['image_file'] === '' and $errors['image_alt'] === '') {

$article['image_file'] = create_filename($_FILES['image']['name'], $uploads);

$destination = $uploads . $article['image_file'];
}
}
$article['title'] = $_POST['title'];
$article['summary'] = $_POST['summary'];
$article['content'] = $_POST['content'];
$article['member_id'] = $_POST['member_id'];
$article['category_id'] = $_POST['category_id'];
$article['published'] = (isset($_POST['published']) and ($_POST['published'] == 1)) ? 1 : 0;


$errors['title'] = is_text($article['title'], 1, 100) ? '' : 'Title must be 1-100 charaters.';
$errors['summary'] = is_text($article['summary'], 1, 254) ? '' :  'Description must be 1-254 characters.';
$errors['content'] = is_text($article['content'], 1, 100000) ? '' : 'Article must be 1-100000 characters.';
$errors['member'] = is_member_id($article['member_id'], $authors) ? '' : 'Please select a profile.';
$errors['category'] = is_category_id($article['category_id'], $categories) ? '' : 'Please select a category.';
$invalid = implode($errors);


if ($invalid) {
$errors['warning'] = 'PLease correct any errors below.';
} else {
$arguments = $article;
try {
    $pdo->beginTransaction();
    if ($destination) {
        $imagick = new \Imagick($temp);
        $imagick->cropTumbnailImage(1200, 700);
        $imagick->writeImage($destination);
        
        $sql = "INSERT INTO image (file, alt) VALUES (:file, :alt);";

        pdo($pdo, $sql, [$arguments['image_file'], $arguments['image_alt'],]);
        $arguments['image_id'] = $pdo->lastInsertId();
    }
    unset($arguments['image_file'], $arguments['image_alt']);
    if ($id) {
        $sql = "UPDATE article
        SET title = :title, summary = :summary, content = :content,
         category_id = :category_id, member_id = :member_id,
         image_id = :image_id, published = :published
         WHERE id = :id;";
    } else {
        unset($arguments['id']);
        $sql = "INSERT INTO article (title, summary, content, category_id,
         member_id, image_id, published)
          VALUES (:title, :summary, :content, :category_id, :member_id,
           :image_id, :published);";
    }
    pdo($pdo, $sql, $arguments);
    $pdo->commit();
    redirect('create1.articlepage.php', ['Succses' => 'article was saved']);   
} catch (PDOException $e) {
$pdo->rollBack();
if (file_exists($destination)) {
unlink($destination);
}
if (($e instanceof PDOException) and ($e->errorInfo[1] === 1062)) {
    $errors['warning'] = 'Article title already exists';
} else {
    throw $e;
  }
}
}
    $article['image_file'] = $saved_image ? $article['image_file'] : '';
}
?>
 <form action="create1.article.php?id=<?= $id ?>" method="POST" enctype="multipart/form-data">
    <main class="container admin" id="content">

      <h1>Edit Article</h1>
      <?php if ($errors['warning']) { ?>
        <div class="alert alert-danger"><?= $errors['warning'] ?></div>
      <?php } ?>

      <div class="admin-article">
        <section class="image">
          <?php if (!$article['image_file']) { ?>
            <label for="image">Upload image:</label>
            <div class="form-group image-placeholder">
              <input type="file" name="image" class="form-control-file" id="image"><br>
              <span class="errors"><?= $errors['image_file'] ?></span>
            </div>
            <div class="form-group">
              <label for="image_alt">Alt text: </label>
              <input type="text" name="image_alt" id="image_alt" value="" class="form-control">
              <span class="errors"><?= $errors['image_alt'] ?></span>
            </div>
          <?php } else { ?>
            <label>Image:</label>
            <img src="../uploads/<?= html_escape($article['image_file']) ?>"
                 alt="<?= html_escape($article['image_alt']) ?>">
            <p class="alt"><strong>Alt text:</strong> <?= html_escape($article['image_alt']) ?></p>
            <a href="alt-text-edit.php?id=<?= $article['id'] ?>" class="btn btn-secondary">Edit alt text</a>
            <a href="image-delete.php?id=<?= $id ?>" class="btn btn-secondary">Delete image</a><br><br>
          <?php } ?>
        </section>

        <section class="text">
          <div class="form-group">
            <label for="title">Title: </label>
            <input type="text" name="title" id="title" value="<?= html_escape($article['title']) ?>"
                   class="form-control">
            <span class="errors"><?= $errors['title'] ?></span>
          </div>
          <div class="form-group">
            <label for="summary">Summary: </label>
            <textarea name="summary" id="summary"
                      class="form-control"><?= html_escape($article['summary']) ?></textarea>
            <span class="errors"><?= $errors['summary'] ?></span>
          </div>
          <div class="form-group">
            <label for="content">Content: </label>
            <textarea name="content" id="content"
                      class="form-control"><?= html_escape($article['content']) ?></textarea>
            <span class="errors"><?= $errors['content'] ?></span>
          </div>
          <div class="form-group">
            <label for="member_id">Author: </label>
            <select name="member_id" id="member_id">
              <?php foreach ($authors as $author) { ?>
                <option value="<?= $author['id'] ?>"
                    <?= ($article['member_id'] == $author['id']) ? 'selected' : ''; ?>>
                    <?= html_escape($author['forename'] . ' ' . $author['surname']) ?></option>
              <?php } ?>
            </select>
            <span class="errors"><?= $errors['author'] ?></span>
          </div>
          <div class="form-group">
            <label for="category">Category: </label>
            <select name="category_id" id="category">
              <?php foreach ($categories as $category) { ?>
                <option value="<?= $category['id'] ?>"
                    <?= ($article['category_id'] == $category['id']) ? 'selected' : ''; ?>>
                    <?= html_escape($category['name']) ?></option>
              <?php } ?>
            </select>
            <span class="errors"><?= $errors['category'] ?></span>
          </div>
          <div class="form-check">
            <input type="checkbox" name="published" value="1" class="form-check-input" id="published"
                <?= ($article['published'] == 1) ? 'checked' : ''; ?>>
            <label for="published" class="form-check-label">Published</label>
          </div>
          <input type="submit" name="update" value="Save" class="btn btn-primary">
        </section>
      </div>
    </main>
  </form>