Your requirements could not be resolved to an installable set of packages. Problem 1 - azjezz/psl[2.3.1, ..., 2.9.0] require ext-intl * -> it is missing from your system. Install or enable PHP's intl extension. - wyrihaximus/async-test-utilities 7.2.0 requires wyrihaximus/test-utilities ^5.5.4 || ^6 -> satisfiable by wyrihaximus/test-utilities[5.5.4, ..., 5.6.0]. - wyrihaximus/test-utilities[5.5.4, ..., 5.6.0] require roave/backward-compatibility-check ^8.3.0 -> satisfiable by roave/backward-compatibility-check[8.3.0, 8.4.0, 8.5.0, 8.6.0]. - roave/backward-compatibility-check[8.3.0, ..., 8.6.0] require azjezz/psl ^2.3.1 -> satisfiable by azjezz/psl[2.3.1, ..., 2.9.0]. - Root composer.json requires wyrihaximus/async-test-utilities ^7.2 -> satisfiable by wyrihaximus/async-test-utilities[7.2.0]. To enable extensions, verify that they are enabled in your .ini files: - C:\tools\php\php.ini You can also run `php --ini` in a terminal to see which files are used by PHP in CLI mode. Alternatively, you can run Composer with `--ignore-platform-req=ext-intl` to temporarily ignore these required extensions. Use the option --with-all-dependencies (-W) to allow upgrades, downgrades and removals for packages currently locked to specific versions.