Add wrapper functions for getting users, objects, and groups that join on that table so that the queries can be ordered by entity type specific columns

[mrclay]

This patch makes it easier to order entity queries by title by adding the necessary join:

$options['order_by'] => 'title'; // now possible
$entities = elgg_get_entities($options);

[mrclay]

patched lib/entities.php from 1.7.4

[mrclay]

Oops, that preg_replace pattern should be:

'/\b(e\.)?title\b/'

Point is to allow user to follow the convention of all order_by columns prefixed with "e.". This might not be a great idea.

[cash]

I think it would be great if Elgg supported sorting by object title, group name, and user name without requiring the developer to write SQL clauses. Perhaps a convenience function to produce the options for elgg_get_entities()?

This patch mixes a convenience option (passing in title) with passing in SQL statements. I think that is a bad precedent. Though elgg_get_entities already mixes these, it hasn't done this with a single parameter.

Options:

• add a sort parameter that handles mapping convenience options to SQL statements
• change order_by to only accept convenience options
• provide a convenience option for a developer to get the necessary SQL statement for a order_by

[ewinslow]

Rels #2527. It doesn't make much sense to me to order by a property that not all of the rows will have, but if I know I just want objects, then it would make sense to join the objects table and allow filtering/sorting based on object-specific fields.

[cash]

I like Evan's idea. Maybe we should look into this for Elgg 1.8 rather than 1.9 as currently marked on #2527. We get a lot of requests for getting an alphabetical list of groups, users, etc.

[ewinslow]

Rels #2675 -- If we implement that, then we won't have to have multiple functions for ordering entities alphabetically depending on their type