The symfony/polyfill-intl-idn is a PHP library that provides a polyfill for the Intl extension's idn_to_ascii and idn_to_utf8 functions. It allows developers to work with Internationalized Domain Names (IDN) in environments where the Intl extension is not available or not compiled with IDN support.

Pros

• Enables IDN functionality without requiring the Intl extension
• Compatible with various PHP versions (5.3.3+)
• Seamless integration with Symfony projects and other PHP applications
• Maintained by the Symfony community, ensuring regular updates and support

Cons

• May have slightly lower performance compared to native Intl extension
• Requires additional installation and configuration steps
• Limited to IDN-specific functions, not a full Intl extension replacement
• Potential compatibility issues with future PHP versions or IDN standards changes

Code Examples

1. Converting a domain name to ASCII:

use Symfony\Polyfill\Intl\Idn\Idn;

$ascii = Idn::idn_to_ascii('mañana.com');
echo $ascii; // Output: xn--maana-pta.com

2. Converting an ASCII domain name back to UTF-8:

use Symfony\Polyfill\Intl\Idn\Idn;

$utf8 = Idn::idn_to_utf8('xn--maana-pta.com');
echo $utf8; // Output: mañana.com

3. Using options for stricter conversion:

use Symfony\Polyfill\Intl\Idn\Idn;

$ascii = Idn::idn_to_ascii('mañana.com', Idn::IDNA_DEFAULT, Idn::INTL_IDNA_VARIANT_UTS46, $info);
echo $ascii; // Output: xn--maana-pta.com
print_r($info); // Additional information about the conversion

Getting Started

To use symfony/polyfill-intl-idn in your project:

1. Install the library using Composer:

   composer require symfony/polyfill-intl-idn
   

2. In your PHP code, use the Idn class:

   use Symfony\Polyfill\Intl\Idn\Idn;
   
   $ascii = Idn::idn_to_ascii('例子.测试');
   $utf8 = Idn::idn_to_utf8('xn--fsqu00a.xn--0zwm56d');
   

The library will automatically provide the idn_to_ascii and idn_to_utf8 functions if they're not available in your PHP environment.