Symfony Polyfill

This project backports features found in the latest PHP versions and provides
compatibility layers for some extensions and functions. It is intended to be
used when portability across PHP versions and extensions is desired.

Polyfills are provided for:

• the apcu extension when the legacy apc extension is installed;
• the ctype extension when PHP is compiled without ctype;
• the mbstring and iconv extensions;
• the uuid extension;
• the MessageFormatter class and the msgfmt_format_message functions;
• the Normalizer class and the grapheme_* functions;
• the utf8_encode and utf8_decode functions from the xml extension or PHP-7.2 core;
• the Collator, NumberFormatter, Locale and IntlDateFormatter classes;
• the intl_error_name, intl_get_error_code, intl_get_error_message and
  intl_is_failure functions;
• the idn_to_ascii and idn_to_utf8 functions;
• the hex2bin function, the CallbackFilterIterator,
  RecursiveCallbackFilterIterator and SessionHandlerInterface classes
  introduced in PHP 5.4;
• the array_column, boolval, json_last_error_msg and hash_pbkdf2
  functions introduced in PHP 5.5;
• the password_hash and password_* related functions introduced in PHP 5.5,
  provided by the ircmaxell/password-compat package;
• the hash_equals and ldap_escape functions introduced in PHP 5.6;
• the *Error classes, the error_clear_last, preg_replace_callback_array and
  intdiv functions introduced in PHP 7.0;
• the random_bytes and random_int functions introduced in PHP 7.0,
  provided by the paragonie/random_compat package;
• the PHP_INT_MIN constant introduced in PHP 7.0,
• the SessionUpdateTimestampHandlerInterface interface introduced in PHP 7.0,
• the is_iterable function introduced in PHP 7.1;
• a Binary utility class to be used when compatibility with
  mbstring.func_overload is required;
• the spl_object_id and stream_isatty functions introduced in PHP 7.2;
• the sapi_windows_vt100_support function (Windows only) introduced in PHP 7.2;
• the PHP_OS_FAMILY constant introduced in PHP 7.2;
• the is_countable function introduced in PHP 7.3;
• the array_key_first and array_key_last functions introduced in PHP 7.3;
• the hrtime function introduced in PHP 7.3;
• the JsonException class introduced in PHP 7.3;
• the get_mangled_object_vars, mb_str_split and password_algos functions
  introduced in PHP 7.4;
• the fdiv function introduced in PHP 8.0;
• the ValueError class introduced in PHP 8.0;
• the FILTER_VALIDATE_BOOL constant introduced in PHP 8.0;

It is strongly recommended to upgrade your PHP version and/or install the missing
extensions whenever possible. This polyfill should be used only when there is no
better choice or when portability is a requirement.

Compatibility notes

To write portable code between PHP5 and PHP7, some care must be taken:

• \*Error exceptions must be caught before \Exception;
• after calling error_clear_last(), the result of $e = error_get_last() must be
  verified using isset($e['message'][0]) instead of null !== $e.

Usage

When using Composer to manage your dependencies, you
should not require the symfony/polyfill package, but the standalone ones:

• symfony/polyfill-apcu for using the apcu_* functions,
• symfony/polyfill-ctype for using the ctype functions,
• symfony/polyfill-php54 for using the PHP 5.4 functions,
• symfony/polyfill-php55 for using the PHP 5.5 functions,
• symfony/polyfill-php56 for using the PHP 5.6 functions,
• symfony/polyfill-php70 for using the PHP 7.0 functions,
• symfony/polyfill-php71 for using the PHP 7.1 functions,
• symfony/polyfill-php72 for using the PHP 7.2 functions,
• symfony/polyfill-php73 for using the PHP 7.3 functions,
• symfony/polyfill-php74 for using the PHP 7.4 functions,
• symfony/polyfill-php80 for using the PHP 8.0 functions,
• symfony/polyfill-iconv for using the iconv functions,
• symfony/polyfill-intl-grapheme for using the grapheme_* functions,
• symfony/polyfill-intl-idn for using the idn_to_ascii and idn_to_utf8 functions,
• symfony/polyfill-intl-icu for using the intl functions and classes,
• symfony/polyfill-intl-messageformatter for using the intl messageformatter,
• symfony/polyfill-intl-normalizer for using the intl normalizer,
• symfony/polyfill-mbstring for using the mbstring functions,
• symfony/polyfill-util for using the polyfill utility helpers.
• symfony/polyfill-uuid for using the uuid_* functions,

Requiring symfony/polyfill directly would prevent Composer from sharing
correctly polyfills in dependency graphs. As such, it would likely install
more code than required.

Design

This package is designed for low overhead and high quality polyfilling.

It adds only a few lightweight require statements to the bootstrap process
to support all polyfills. Implementations are then loaded on-demand when
needed during code execution.

If your project requires a minimum PHP version it is advisable to add polyfills
for lower PHP versions to the replace section of your composer.json.
This removes any overhead from these polyfills as they are no longer part of your project.
The same can be done for polyfills for extensions that you require.

If your project requires php 7.0, and needs the mb extension, the replace section would look
something like this:

{
    "replace": {
        "symfony/polyfill-php54": "1.99",
        "symfony/polyfill-php55": "1.99",
        "symfony/polyfill-php56": "1.99",
        "symfony/polyfill-php70": "1.99",
        "symfony/polyfill-mbstring": "1.99"
    }
}

Polyfills are unit-tested alongside their native implementation so that
feature and behavior parity can be proven and enforced in the long run.

License

This library is released under the MIT license.