Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires typo3/testing-framework dev-main -> satisfiable by typo3/testing-framework[dev-main]. - ssch/typo3-rector[v1.4.0, ..., v1.7.0] require nikic/php-parser ^4.17 -> satisfiable by nikic/php-parser[v4.17.0, ..., v4.19.4]. - ssch/typo3-rector[v1.0.0, ..., v1.3.6] require nikic/php-parser ^4.14 -> satisfiable by nikic/php-parser[v4.14.0, ..., v4.19.4]. - You can only install one version of a package, so only one of these can be installed: nikic/php-parser[v4.10.4, ..., v4.19.4, v5.0.0, ..., v5.3.1]. - Conclusion: don't install one of nikic/php-parser[v5.3.1], ssch/typo3-rector[v1.8.1] (conflict analysis result) - Conclusion: install nikic/php-parser v5.3.1 (conflict analysis result) - Root composer.json requires ssch/typo3-rector ^1 -> satisfiable by ssch/typo3-rector[v1.0.0, ..., v1.8.1].