Add PHP Architecture Tester

README.md

 * [Deptrac](https://github.com/sensiolabs-de/deptrac) - A static code analysis tool that helps to enforce rules for dependencies between software layers.
 * [Mondrian](https://github.com/Trismegiste/Mondrian) - A code analysis tool using Graph Theory.
 * [phan](https://github.com/phan/phan) - A static analyzer based on PHP 7+ and the php-ast extension.
+* [PHP Architecture Tester](https://github.com/carlosas/phpat) - Easy to use architecture testing tool for PHP.
 * [PHPCompatibility](https://github.com/PHPCompatibility/PHPCompatibility) - A PHP compatibility checker for PHP CodeSniffer.
 * [PhpDependencyAnalysis](https://github.com/mamuz/PhpDependencyAnalysis) - A tool to create customisable dependency graphs.
 * [PHP Metrics](https://github.com/phpmetrics/PhpMetrics) - A static metric library.