Challenge 2 — Solution

Task: Write a queueJob(PDO $pdo, string $type, array $payload) function
that inserts a new pending job with a JSON-encoded payload, generalising
the chapter's queueEmail() to handle any job type. Then show how it
would be called for two different job types: 'send_email' and
'resize_image'.

<?php
    function queueJob(PDO $pdo, string $type, array $payload) {
        $stmt = $pdo->prepare("INSERT INTO jobs (type, payload, status) VALUES (:type, :payload, 'pending')");
        $stmt->execute([
            'type' => $type,
            'payload' => json_encode($payload)
        ]);
    }

    // Called for a "send_email" job:
    queueJob($pdo, 'send_email', [
        'to' => 'sam@example.com',
        'subject' => 'Welcome!'
    ]);

    // Called for a "resize_image" job:
    queueJob($pdo, 'resize_image', [
        'source_path' => '/uploads/photo_original.jpg',
        'target_width' => 800,
        'target_height' => 600
    ]);
?>


Output:
(No direct output — both calls insert a new row into the jobs table,
each with its own $type value and a JSON-encoded $payload matching
that job's own specific data needs.)

Notes:
- queueJob() generalises the chapter's own queueEmail() by accepting
  $type as a genuine parameter rather than hardcoding 'send_email' in
  the SQL, and by accepting a plain $payload array rather than
  separate $to/$subject parameters - letting it handle any job's own
  arbitrarily-shaped data.
- Both example calls pass a completely different payload shape
  (to/subject for email, source_path/target_width/target_height for
  image resizing) - exactly demonstrating why payload is stored as
  flexible JSON text rather than fixed database columns, per Challenge
  1's own reasoning.
- The prepared statement with named placeholders (:type, :payload)
  reuses the exact SQL-injection-safe pattern from Intermediate
  Chapter 4, applied here to job-queue data rather than user-facing
  form data.