A feed-to-JSON service becomes easier to maintain when it has a narrow job: retrieve an approved feed, interpret its supported fields, and publish a predictable record. PHP can do that work, but XML parsing is only one part of the boundary. Network access, resource limits, identity, content handling, and failure reporting deserve explicit decisions before the first endpoint is exposed.

This guide describes a small RSS 2.0 adapter for a controlled collection of publishers. Use the implementation plan as a starting point for your own adapter, with deliberately limited format support. Start with the Pro RSS PHP guide if you need the wider architecture. Here, the goal is to make the contract small enough that another developer can understand what goes in, what comes out, and what happens when a publisher sends something unexpected.

Define the JSON contract first

Choose a modest set of output fields: source identifier, item identifier, title, canonical link, publication date, summary text, and observation time. Include a schema version so consumers can distinguish later changes. Decide which values may be absent. A missing publication date should remain missing; replacing it with the current time turns an unknown date into a false claim about the article.

Keep publisher data separate from collection metadata. The publisher's date describes the item, while your fetch timestamp describes your own observation. Similarly, a feed title is a publisher label, while a source identifier belongs to your configuration. This distinction lets you rename a source in your dashboard without changing the identity of every item it has already supplied.

Write one example record and one error record before implementing the parser. Ask a consumer to explain both back to you. If the consumer cannot tell an empty feed from a failed refresh, the contract needs another status field. The Pro RSS API design page discusses these interface choices in the context of downstream applications.

Separate fetching from parsing

For a small installation, keep approved feed addresses in configuration and accept a source identifier at the application boundary. This avoids turning an RSS endpoint into an unrestricted URL fetcher. Permit only the network protocols your design requires. Keep TLS verification enabled, set connection and overall timeouts, and limit both the transferred response and its decoded size. A compressed response can grow substantially after decompression.

Validate destinations before connecting. An allowlist must be applied to redirects as well as initial addresses, and hostname approval must not permit connections to private or otherwise prohibited network addresses through DNS resolution. Keep redirects disabled until the client can enforce those rules correctly. Network egress controls provide another useful boundary. These responsibilities belong in the downloader, not in XML parser options.

Record the final approved address, response status, and retrieval time. Check for an unsuccessful HTTP response before trying to interpret its body as a feed. An HTML error page may be perfectly valid text while still being the wrong input. Store a bounded diagnostic sample privately when needed, with credentials and sensitive addresses removed.

Use explicit XML settings

The PHP manual for libxml constants documents the distinction between disabling parser network access and controlling external entities. LIBXML_NONET disables network access while loading documents. LIBXML_NO_XXE is available with PHP 8.4 and libxml 2.13 or later. Avoid enabling DTD loading, DTD validation, or entity substitution for this adapter, and do not raise parser limits with LIBXML_PARSEHUGE to accommodate untrusted input.

The following fragment illustrates only the parse stage. It assumes the downloader has already returned a bounded byte string. It deliberately requires the newer external-entity control instead of silently changing behavior on an older runtime. The runtime itself still needs a supported, maintained PHP and libxml installation.

if (!defined('LIBXML_NO_XXE')) {
    throw new RuntimeException('Required XML protection unavailable');
}
if (strlen($bytes) > 2_000_000) {
    throw new RuntimeException('Feed exceeds the application limit');
}
$previous = libxml_use_internal_errors(true);
try {
    $xml = simplexml_load_string(
        $bytes,
        SimpleXMLElement::class,
        LIBXML_NONET | LIBXML_NO_XXE
    );
    if ($xml === false) {
        throw new RuntimeException('Feed XML could not be parsed');
    }
} finally {
    libxml_clear_errors();
    libxml_use_internal_errors($previous);
}

The two-megabyte limit is an example application policy, not an RSS requirement. Choose limits using representative feeds and available resources. The strict comparison with false matters because a SimpleXML object can behave unexpectedly in a loose Boolean check. Collect useful parser diagnostics before clearing the error buffer, but expose a stable application error to consumers instead of raw parser output.

Recognize the supported format deliberately

After parsing, check that the document is the expected RSS 2.0 structure before iterating its channel items. XML being well formed does not make it an RSS feed. Return an explicit unsupported-format result for Atom or another feed dialect until you add a tested adapter. Avoid guessing that every document with repeated title elements represents the same data model.

Map fields individually and cast the values you need to strings. Do not serialize the entire SimpleXML object directly and call the result your API. An explicit mapping gives clients consistent shapes and prevents unfamiliar extension elements from unexpectedly appearing in output. Define an item-count limit and a text-length policy alongside the byte limit, then record when either policy excludes content.

Preserve identity and uncertainty

Use a publisher's item identifier within the scope of its source. If it is absent, a documented fallback can use the item link, provided your application records how that fallback was chosen. Avoid using titles as permanent identifiers because publishers can edit them. Treat content hashes as revision signals; they are usually poor substitutes for stable identity when an item receives a correction.

Parse dates with a defined policy, preserve the original date string for diagnostics, and use a null value when interpretation fails. Validate item links against permitted schemes before returning them for display. If you support relative addresses, resolve them with a standards-aware URL library and an explicit base. Do not use string concatenation to assemble addresses.

Keep imported HTML outside the trust boundary

For the first version, return a plain-text summary with a documented maximum length. If the product later needs rich HTML, introduce a maintained allowlist sanitizer and test its actual configuration. XML parsing does not make embedded markup suitable for insertion into a web page. Escape text when rendering it in HTML, and treat link destinations and other attributes according to their own contexts.

Do not automatically fetch every image, enclosure, or link mentioned in an item. Each extra request expands the downloader's responsibilities and changes operating cost. Store the relevant reference first, then define a separate policy for any enrichment. This keeps a feed refresh from quietly becoming a crawler.

Define a policy for incomplete items

Treat an absent optional field differently from an unreadable document. If your schema permits an unknown date, keep the item and return a null date. If it requires a usable article link, an item without one should follow a documented exclusion policy. Avoid repairing missing values by inventing plausible replacements. A consumer cannot recover the original uncertainty after the adapter has replaced it with a fabricated value.

If partial results are allowed, return counts for items inspected, accepted, and excluded, alongside a bounded list of reason codes. Keep those codes stable so a dashboard can distinguish missing fields from unsupported content. An entirely rejected feed should not look like a successful empty feed. This makes source-quality changes visible without forcing every consumer to inspect private processing logs.

Cache the last good result and test failures

When a publisher supplies HTTP validators, use conditional requests and interpret a not-modified response as permission to reuse the stored representation. Publish a new snapshot only after fetching, parsing, and normalization succeed. Keep the last successful snapshot during a temporary failure, while exposing its age and the failed refresh status. Never label stale data as freshly retrieved.

Build fixtures for malformed XML, unsupported formats, missing titles, invalid dates, duplicate identifiers, large fields, HTML content, and redirects to prohibited destinations. Test network policy independently from parser behavior. Verify that a failed item or feed follows the contract you wrote at the beginning, including whether partial results are allowed. A happy-path sample alone cannot demonstrate that this boundary is reliable.

Keep the adapter small enough to explain

A useful PHP feed adapter has a clear input policy, a predictable output schema, and visible failure states. Expand format support only when a real source requires it, and add a fixture with each new mapping. Document these decisions alongside the service using the Pro RSS documentation checklist. The strongest first release is one whose limits are explicit and whose consumers can distinguish source facts from processing decisions.