Polyfill Intl Idn Laravel Package

Getting Started

Install the package via Composer:

composer require symfony/polyfill-intl-idn

It’s automatically autoloaded—no manual setup or config required. The polyfill registers idn_to_ascii() and idn_to_utf8() functions globally only if they don’t already exist (i.e., when ext-intl is absent).
First use case: Sanitize user-submitted international domains for storage or validation:

$domain = idn_to_ascii('москва.рф'); 
// → 'xn--80acaazcfs.xn--p1ai'

Implementation Patterns

• Drop-in Replacement for Native Functions: Call idn_to_ascii()/idn_to_utf8() directly anywhere—no namespace imports. Works identically to ext-intl when available.
• Input Normalization Pipeline: Integrate into form request validation or middleware to convert Unicode domains to ASCII before DB storage or comparison:

  $normalized = idn_to_ascii($input['domain'] ?? '');
  if ($normalized === false) {
      // Handle invalid domain
  }
  

• Dual Conversion Workflow: Use idn_to_ascii() for storage/comparison and idn_to_utf8() for UI display—ensures both safety and readability:

  $ascii = idn_to_ascii($domain); // Stored in DB
  $ui = idn_to_utf8($ascii);      // Shown in profile view
  

• Compliance Validation Stack: Chain with filter_var(..., FILTER_VALIDATE_DOMAIN, FILTER_FLAG_HOSTNAME) after ASCII conversion for robust RFC-compliant validation.

Gotchas and Tips

• Silent Failures: idn_to_ascii() returns false and triggers E_WARNING on invalid input (e.g., malformed labels). Use @idn_to_ascii() or check intl_get_error_code() (if ext-intl is present) for graceful handling.
• Contextual Flags: Default behavior (IDNA_DEFAULT) may not suit all cases. For email addresses (RFC 6142), explicitly set flags:

  idn_to_ascii('test@café.com', IDNA_CHECK_BIDI | IDNA_NONTRANSITIONAL_TO_ASCII);
  

• Dependency Order: Requires symfony/polyfill-intl-normalizer. Composer handles this automatically—verify composer.lock isn’t stale if IDN calls fail silently.
• Environment Awareness: Even in ext-intl-enabled environments, include the polyfill for consistency across dev/staging/prod (avoids "works on my machine" edge cases). The polyfill safely self-deactivates if native functions exist.
• Avoid Overuse: Not suitable for DNS validation, MX record lookups, or complex locale-aware IDN handling—reserve for ASCII/Unicode domain translation only.