Question

the PHP mysqli_result class implements the Traversable interface for some time now.
This gives some interesting possibilities like the following piece of code:

<?php

$db = new mysqli( '...' );

$result = $db->query( '...' );

foreach( $result as $row ) {
   //$row is an associative array containing the fetched values
}

Now, I like this pretty much, but in the library I am currently working on I would like to have objects fetched, not associative arrays. I also want to be able to pass a class to it, so I can create a simple model system with it

For that I extend it like this:

<?php

class mysqli_result_extension extends mysqli_result {

    protected $result_class;

    public function set_result_class( $class ) { $this->result_class = $class; }

    public function function_to_overwrite() {

        return $this->fetch_object( $this->result_class );
    }
}

My problem and my question to you:

How do I switch from fetch_assoc to fetch_object now?
I would like to overwrite the method the Traversable interface uses in order to return the result, but it doesn’t define any (http://php.net/manual/en/class.traversable.php)

So what would I need to overwrite in order to switch from fetch_assoc to fetch_object and to be able to pass my $result_class to it so I am able to do something like this:

<?php

$db = new mysqli_extension( '...' );

$posts = $db->query( 'select * from posts' );
//$result is object of type mysqli_result_extension

$posts->set_result_class( 'post' );

foreach( $posts as $post ) {
   //$post is an instance of class 'post'
}

I don’t want something dirty, hacky like overwriting fetch_assoc and just returning the object in it

Thanks in advance for your help and input

Answer 1

As I stated in the comments, it’s easy to do exactly what you want with PDO. Just set the PDO::ATTR_DEFAULT_FETCH_MODE attribute, and it will do the appropriate kind of fetch when you do the foreach loop.

You can also set the PDO::ATTR_STATEMENT_CLASS attribute to define the class to use.

$pdo->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_CLASS);
$pdo->setAttribute(PDO::ATTR_STATEMENT_CLASS,array('classname',$constructorArgs));

See http://php.net/manual/en/pdo.setattribute.php for more info.

With that solution, you’d need to change the ATTR_STATEMENT_CLASS attribute for each query, depending on what class you want to instantiate.

Alternatively, you can set it to specify the classname within the query:

$db->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_CLASS | PDO::FETCH_CLASSTYPE);
$stmt = $db->query("SELECT 'classname', * FROM `table` WHERE `id` = 1;");

Simply add the relevant classname to your query as the first field to be selected.

See one of the answers on this related question In PHP, How do I set default PDO Fetch Class? for more on this.