world-game/site/templates/portfolio.json.php

<?php

$specificData = [
  'projects' => $page->children()->listed()->map(function($project) {
    return [
      'title'          => $project->title()->value(),
      'slug'           => $project->slug(),
      'catchphrase'    => $project->catchphrase()->value(),
      'description'    => $project->description()->value(),
      'thumbnail'      => $project->thumbnail()->toFile()?->url(),
      'images_gallery' => $project->images_gallery()->toFiles()->map(fn($f) => $f->url())->values(),
      'mockup'         => $project->mockup()->toFile()?->url(),
      'keywords'       => $project->keywords()->toStructure()->map(fn($i) => [
                            'label' => $i->label()->value(),
                            'text'  => $i->text()->value(),
                          ])->values(),
      'external_links' => $project->external_links()->toStructure()->map(fn($i) => [
                            'label' => $i->label()->value(),
                            'url'   => $i->url()->value(),
                          ])->values(),
    ];
  })->values()
];

$pageData = array_merge($genericData, $specificData);

header('Content-Type: application/json');
echo json_encode($pageData);