Drupal: How can I run a custom function every time a user posts a comment?

I'm using Drupal 6 and its core comment module.

I want to run a custom funcion every time a user posts a comment, but 开发者_Python百科I don't want to mess with the comment.module for obvious reasons.

Is there a practical way I can do this in a custom module? If not, what are the alternatives as I don't want to write my own commenting system.

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The Drupal core api provides a hook for interacting with comments.
See http://api.drupal.org/api/function/hook_comment

Implement hook_comment in your custom module's .module file.
For example:

/**
 * Implementation of hook_comment().
 */
function modulename_comment(&$a1, $op) {
  switch ($op) {
    case 'insert':
      // Call custom function here.
      break;
  }
}

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Perhaps an easier way is to setup a trigger and action using the trigger module.