Building a Headless CMS API with ProcessWire

Organizing Content Delivery via ProcessWire API

A ProcessWire project has been running for several years, with dozens of templates accumulated. Then the client demands a React SPA or mobile app. Standard PHP rendering won't work—they need clean JSON. You could hack together something with direct DB access, but that breaks permission logic and caching. The right solution is to add an HTTP API on top of the existing templates. We do this in 2–4 days using built-in tools: a template router or the GraphQL module. No rewriting—just a new endpoint.

We have completed over 30 such projects. The most loaded configuration handles up to 100,000 requests per day on a budget VPS. The API has been running without issues for over two years. Below we break down the implementation options.

Built-in PHP API

ProcessWire exposes $pages, $page, $user, and $config as global variables in templates:

// templates/blog.php // Selection with filters and pagination $limit = 12; $start = ($input->pageNum - 1) * $limit; $posts = $pages->find("template=blog-post, status=published, sort=-date, limit=$limit, start=$start"); $totalPosts = $pages->count("template=blog-post, status=published"); // Selection with field conditions $featuredPosts = $pages->find(" template=blog-post, featured=1, date>=today, category.name%=Web Development, sort=-date, limit=3 "); // Single item $post = $pages->get("template=blog-post, slug=my-post-slug"); if (!$post->id) wire404(); 

For a full ProcessWire JSON API, we create custom REST endpoints using ProcessWire API templates, enabling seamless headless ProcessWire SPA development.

Selector String — Query Language

// Text search $pages->find("template=product, title*=laptop, sort=title"); // Numeric conditions $pages->find("template=product, price>=1000, price<=5000"); // Date $pages->find("template=event, event_date>=today, sort=event_date"); // OR conditions $pages->find("template=post, (category=tech|category=science)"); // Related pages $pages->find("template=product, categories.id={$category->id}"); // Full-text search $pages->find("title|body~=search query, template=post"); // Sort by custom field $pages->find("template=product, sort=-rating, sort=title"); 

REST API via ProCache or Custom Module

ProcessWire does not ship with a built-in REST API. We create one using a template router:

// site/templates/api.php // URL: /api/blog/?page=1&limit=10 header('Content-Type: application/json'); header('Access-Control-Allow-Origin: ' . $config->httpHost); // Simple key-based authorization $apiKey = $input->get->text('key'); if ($apiKey !== $config->apiKey) { http_response_code(401); echo json_encode(['error' => 'Unauthorized']); return; } $page_num = (int) $input->get->int('page') ?: 1; $limit = min((int) $input->get->int('limit') ?: 10, 100); $start = ($page_num - 1) * $limit; $posts = $pages->find(" template=blog-post, status=published, sort=-date, limit=$limit, start=$start "); $result = [ 'data' => array_map(fn($post) => [ 'id' => $post->id, 'title' => $post->title, 'slug' => $post->name, 'url' => $post->url, 'date' => $post->date->format('Y-m-d'), 'excerpt' => $post->excerpt, 'image' => $post->image ? [ 'url' => $post->image->width(800)->url, 'width' => 800, 'height' => (int) round(800 / $post->image->ratio), ] : null, ], $posts->getArray()), 'total' => $posts->getTotal(), 'page' => $page_num, 'limit' => $limit, ]; echo json_encode($result); 

ProcessWire GraphQL Module

Install via ProcessWire modules. Download from processwire.com/modules/processwire-graphql/ and add settings to config.php:

$config->graphql = [ 'templateFilters' => ['blog-post', 'product', 'category'], 'fieldFilters' => ['title', 'body', 'date', 'image', 'category'], 'maxLimit' => 100, ]; query { blogPost(s: "status=published, sort=-date, limit=10") { list { id title date body image { url(width: 800) } category { title url } } total } } 

Response Caching

// Caching via WireCache $cacheKey = "api_posts_page{$page_num}"; $cached = $cache->get($cacheKey); if ($cached) { echo $cached; return; } // ... build $result ... $json = json_encode($result); $cache->save($cacheKey, $json, 3600); // 1 hour echo $json; 

Building a basic REST API on ProcessWire (5–7 endpoints) takes 2–4 days. Typical investment: a basic REST API starts at $2,500, including caching and documentation. GraphQL integration adds $500–$1,500. Cost is determined after analyzing the project scope. Typical costs range from $3,000 to $5,000, and our approach saves you 30–40% compared to alternative CMS migrations.

REST vs GraphQL for ProcessWire

REST is better when you need minimal response and full control. GraphQL is preferable if clients need flexible field selection.

ProcessWire as a Headless CMS: Advantages

Unlike WordPress (where an API is a bolt-on hack) or Strapi (heavy), ProcessWire provides a single source of truth for both PHP templates and external clients. You write templates once, and the JSON output is just a second template with different headers. According to our estimates, this reduces maintenance costs by 30–40%.

ProcessWire API documentation confirms that selectors work identically in templates and API.

What Is Included in ProcessWire API Setup

Deliverables:

• API documentation (Postman/OpenAPI)
• Access to staging environment
• 1-hour training session for your developers
• 30 days of post-deployment support
• Source code and deployment scripts