[6.4] Understand Polyfill detection

[llaville]

With PHP CompatInfo 6.4.0, a new feature was added to be awareness of compatibility packages

When you install CompatInfo 6.4 on PHP 7.4 plateform, you should have these following dependencies installed too :

symfony/polyfill-ctype             v1.25.0            Symfony polyfill for ctype functions
symfony/polyfill-intl-grapheme     v1.25.0            Symfony polyfill for intl's grapheme_* functions
symfony/polyfill-intl-normalizer   v1.25.0            Symfony polyfill for intl's Normalizer class and related functions
symfony/polyfill-mbstring          v1.25.0            Symfony polyfill for the Mbstring extension
symfony/polyfill-php72             v1.25.0            Symfony polyfill backporting some PHP 7.2+ features to lower PHP versions
symfony/polyfill-php73             v1.25.0            Symfony polyfill backporting some PHP 7.3+ features to lower PHP versions
symfony/polyfill-php80             v1.25.0            Symfony polyfill backporting some PHP 8.0+ features to lower PHP versions
symfony/polyfill-php81             v1.25.0            Symfony polyfill backporting some PHP 8.1+ features to lower PHP versions

So, when you run analyser:run command on following snippet source code,

<?php

var_dump(mb_chr(128024, 'UTF-8'));

var_export(enum_exists('suit'));

print_r(mb_list_encodings());

var_export(ctype_alnum('foo!#$bar'));

print ICONV_VERSION;

you should get such Polyfill analysis results :

What does it means ?

• ICONV_VERSION constant is detected as a polyfill because Bartlett\CompatInfo\Application\Polyfills\SymfonyIconv service is loaded by default configuration, but no version is affected because symfony/polyfill-iconv dependency is not installed.

• ctype_alnum function is detected as a polyfill because Bartlett\CompatInfo\Application\Polyfills\SymfonyCtype service is loaded by default. Version is affected (PHP 7.1.0 min) because symfony/polyfill-ctype dependency v1.25.0 is installed.

• mb_chr function is detected as a polyfill by two different loaded services (Bartlett\CompatInfo\Application\Polyfills\SymfonyPhp72, Bartlett\CompatInfo\Application\Polyfills\SymfonyMbstring). Version is also affected because symfony/polyfill-mbstring dependency v1.25.0 and symfony/polyfill-php72 dependency v1.25.0 are installed.