[wp-trac] [WordPress Trac] #25429: `get_the_category_by_ID` triggers PHP notice on non-existent category

[WordPress Trac]

#25429: `get_the_category_by_ID` triggers PHP notice on non-existent category
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 Reporter:  ericmann                |       Owner:
     Type:  defect (bug)            |      Status:  new
 Priority:  normal                  |   Milestone:  3.7
Component:  Taxonomy                |     Version:  2.3
 Severity:  normal                  |  Resolution:
 Keywords:  has-patch dev-feedback  |
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Comment (by ericmann):

 Replying to [comment:3 johnbillion]:
 > Should we match `get_tag()` for consistency by returning `null`, or
 should we return a `wp_error` as per Sergey's patch?

 Took some time to think about this, and I agree that since `get_tag()`
 returns `null`, then `get_category()` should do the same.  However,
 `get_the_category_by_ID()` erring when `get_category()` returns null is
 still a problem, so I've moved Sergey's error call higher up the stack.

 Some code in production might already be counting on
 `get_tag()`/`get_category()` returning null for nonexistent categories.
 Anyone doing an `if ( null === get_category( $something ) )` check would
 see a lot of huge issues if we suddenly start returning `WP_Error`
 instead.  But since `get_the_category_by_ID()` will currently break with a
 bad category, we should do the `null` check inside there to prevent
 explosions.

 Patch 25429.3 adds Sergey's docblock edits to `get_category()` and also
 adds a `null` check to `get_the_category_by_ID()`.  Method returns aren't
 changed, but this will fix the PHP notice reported above.

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Ticket URL: <http://core.trac.wordpress.org/ticket/25429#comment:4>
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