How to use try-catch block for PDO

问题

What is a decent way to handle PDO error when using try catch block?

Currently I have something like this:

BlogModel.php

   class BlogModel extends Model {
       public function save($id, $value) {
         $stmt = $this->getDb()->prepare('UPDATE setting SET name = :name WHERE id = :id');
         $stmt->bindParam(':id', $id);
         $stmt->bindParam(':name', $values);
         return ($stmt->execute() !== false) ? $id : false;
       }
   }

So, in the controller BlogController.php, I would do something like this:

<?php
class Blog extends Controller {

    public function comments()
    {
        $data = array();
        $model = new BlogModel;

        if ($model->save(2,'test')) {
                $data['result']['message'] = 'Settings saved';
                $data['result']['status'] = 'success';
        } else {
                $data['result']['message'] = 'Could not save the settings';
                $data['result']['status'] = 'error';
        }

        $view = new View("view.php", $data)
        $view->render();
    }
}
?>

This is the way I handle PDO error using if conditions. What is the decent way to translate this into try catch block? I don't want to code the variables ($data['result']['message'] $data['result']['status']) all the time.

Is possible to add "throw exception" in the catch block somehow?

If there is a lot of try catch blocks in the controller, it going to look messy.. right?

回答1:

None of the answers here are wrong. But actually all three combined are the real answer. You should definitely set

$this->pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

as said by Cerad.

From now on every single issue about anything regarding database is thrown via exception of type PDOException. You just don't have to throw your own Exception as said by ladar because it's useless. Just take the ladar code and convert it into

 ...
 $data = array();
 $model = new BlogModel;

    try{
      $model->save(2,'test');
      $data['result']['message'] = 'Settings saved';
      $data['result']['status'] = 'success';
    }catch(PDOException $e){
        $data['result']['message'] = 'Could not save the settings';
        $data['result']['status'] = 'error';
    }

And do NOT throw anything by yourself.

Then a very nice way for debugging PDO queries is using the catch script linked by Basic that you can find here once again.

Combining this things togheter you'll have a flexible, clean and easy-debug way to catch all the errors that could come.

回答2:

What about:

class BlogModel extends Model {
   public function save($id, $value) {
   ...
   if (!$stmt->execute()) {
        throw new Exception($stmt->errorInfo());
    }
   return $id;

And then

 ...
 $data = array();
 $model = new BlogModel;

    try{
      $model->save(2,'test');
      $data['result']['message'] = 'Settings saved';
      $data['result']['status'] = 'success';
    }catch(Exception $e){
        $data['result']['message'] = 'Could not save the settings';
        $data['result']['status'] = 'error';
    }

回答3:

Have you considered letting PDO itself throw exceptions instead of errors?

$this->pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

Now you can eliminate checking PDO errors which can significantly reduce code. You can add some try/catch block to catch exceptions that can be recovered from such as constraint violations.

For the rest just use a Try/Catch somewhere high up in your front end controller to catch the truly exceptional exceptions.

The only difference in my approach is that in BlogModel you just:

$stmt->execute();

No checking or anything else. Just let PDO throw an exception if the insert fails. Then you would use the try/catch in your controller as shown by ladar

Or in my case, if I was pretty sure the insert would never fail then I'd just use a generic try/catch block up in my front controller and not spend time trying to handle each possible exception manually.

来源：https://stackoverflow.com/questions/9252276/how-to-use-try-catch-block-for-pdo

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php

mysql

pdo

try-catch