When posting to Blogger, it's useful to organize your posts using using labels. When using the normal Blogger interface, this is done by adding a comma-separated list of labels to a text field at the bottom of the post. To achieve the same effect using the Blogger API, add an individual <atom:category> element for each label to your post's entry. Set the scheme to 'http://www.blogger.com/atom/ns#', and set the term to your desired label.
For example, the following code for the Zend_Gdata PHP client library would add the labels "foo" and "bar" to a post (stored in $entry):
$label1 = new Zend_Gdata_App_Extension_Category(
'foo', 'http://www.blogger.com/atom/ns#');
$label2 = new Zend_Gdata_App_Extension_Category(
'bar', 'http://www.blogger.com/atom/ns#');
$entry->setCategory(array($label1, $label2));
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