PHP命名空间未被识别，使用PHP-ML无输出问题求助

Hey there! I’ve been where you are—staring at a blank screen after running a PHP-ML example, with zero errors to point me in the right direction. Let’s walk through the most common fixes step by step:

• First, force PHP to show all errors immediately
  PHP hides errors by default in most environments, which makes silent failures impossible to debug. Add these lines at the VERY TOP of your index file:

  error_reporting(E_ALL);
  ini_set('display_errors', 1);
  ini_set('display_startup_errors', 1);
  

  Run your script again—this will almost certainly reveal a missing dependency, syntax typo, or version mismatch you couldn’t see before.

• Double-check Composer installation & autoloading
  PHP-ML relies entirely on Composer to load its classes. Make sure:

  1. You ran composer install (or composer require php-ai/php-ml) in your project root to pull in the library files.
  2. You’re including the autoloader at the start of your script:

     require_once __DIR__ . '/vendor/autoload.php';
     

  Forgetting the autoloader is the #1 mistake new PHP devs make with Composer-based libraries—without it, PHP can’t find any PHP-ML classes, but might fail silently if error reporting is disabled.

• Verify your namespace usage
  All PHP-ML classes live under the Phpml namespace. If you’re using a class like KNearestNeighbors, you either need to:

  • Add a use statement at the top of your file:

    use Phpml\Classification\KNearestNeighbors;
    

  • Or reference the full qualified class name every time you instantiate it:

    $classifier = new \Phpml\Classification\KNearestNeighbors();
    

  A missing or misspelled namespace will cause PHP to fail to load the class, leading to that frustrating blank screen.

• Don’t forget to output your results!
  It sounds obvious, but I’ve caught myself doing this too! If your example code only trains a model and runs a prediction but doesn’t print the result, you’ll see nothing. Add an echo, var_dump, or print_r to display what the model returns:

  $prediction = $classifier->predict(['your-feature-data-here']);
  var_dump($prediction); // This line is critical to see your output!
  

• Check your PHP version compatibility
  The v0.1.0 release of PHP-ML requires PHP 7.0 or higher. If you’re running an older version (like PHP 5.x), the library won’t work at all—and again, you might not see errors if reporting is turned off. Run php -v in your terminal to confirm your PHP version.

If you work through these steps, you’ll almost certainly find the root cause. Start with enabling error reporting—it’s the fastest way to stop guessing and start fixing!

内容的提问来源于stack exchange，提问作者Connor Kurschat