One of the quickest and minimal code quality checks in software development is a simple syntax check. In case of PHP we have
php -l <path/to/file.php>, nothing smart, nothing fancy.
In case of check automation or continuous integration you even may use Phing task PhpLintTask – runs perfectly and fails build f someone occasionally commits code with syntax errors.
But if you have many files, many CPU cores and fast enough disk – you can lint your PHP files in parallel with PHP Parallel Lint. I’ve tried this tool today and it runs twice faster than standard Phing task using serial approach.