[wp-trac] [WordPress Trac] #9953: Use Dependency Injection for wpdb Connectors

[WordPress Trac]

#9953: Use Dependency Injection for wpdb Connectors
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 Reporter:  jacobsantos   |       Owner:            
     Type:  defect (bug)  |      Status:  new       
 Priority:  normal        |   Milestone:  Unassigned
Component:  General       |     Version:            
 Severity:  normal        |    Keywords:            
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 I think I might have written about this before and I apologize about bring
 it up again, but I'm interested in this again.

 Right now, to use mysqli or PDO, you would have to write your own class
 that replaces wpdb completely. The reason for this is that all classes are
 going to use wpdb. You could also update $wpdb, but this isn't the best
 solution because you are still required to implement all of the methods in
 wpdb and keep them updated.

 The solution I propose is to use Dependency Injection pattern and instead
 of using straight mysql calls, call a class that has the functions in a
 wrapper. I would suggest removing debugging and error calls as well and
 separating them out into their own classes and using the same DI pattern
 as well for them (it is slightly more difficult to do so for debugging and
 failure use cases, perhaps including a function if it exists to replace
 the default one?).

 This can be implemented and compatible with PHP4 (it would be with so much
 hate that it would be done so). I would also go as so far as to have
 implementations for mysqli and PDO as well for if the user wishes to use
 them instead.

 The implementation would look something like this:

 {{{
 #!php
 <?php
 function change_dependency()
 {
     global $wpdb;

     $wpdb->connector( new My_Wpdb_Connector() );
 }
 }}}

 If it was a plugin.

 If you want to use the defaults, I'll suggest an constant:

 {{{
 #!php
 <?php
 if( defined('WP_USE_MYSQLI') )
     $wpdb->connector( new WordPress_Connector_Mysqli() );
 else if( defined('WP_USE_PDO') )
     $wpdb->connector( new WordPress_Connector_Pdo() );
 else
     $wpdb->connector( new WordPress_Connector_MySql() );
 }}}

 in wpdb.php. You could also check for PDO extension, the MySQLi extension,
 and use one, if it exists. I will say that allowing the user to choose is
 a better choice, since there might be a really good reason to not use PDO
 and instead use MySQLi.

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Ticket URL: <http://core.trac.wordpress.org/ticket/9953>
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