term_exists returns 0 and null

[barrykooij]

The function term_exists in wp-includes/taxonomy.php has two different return values, 0 and null. The function does a few checks and returns 0 if the condition of the check is not met. If the checks are met, the return value will be the result of a $wpdb->get_row or $wpdb->get_var. If the term is not found in the database the methods get_row and get_var will return null.

Because of the different type of return values it's not possible to do a strict check on the return value to see if a term was found. I've changed the return 0 in term_exists to return null, so that if there is no term found the result of term_exists will always be null.

[barrykooij]

Taxonomy Patch

[ocean90]

Should probably do the same with post_exists.

[barrykooij]

Replying to ocean90:

Should probably do the same with post_exists.

Thanks, created a new ticket for this. Please see #21607

[scribu]

You can upload another patch on this ticket, since it seems similar enough.

[SergeyBiryukov]

Because of the different type of return values it's not possible to do a strict check on the return value to see if a term was found.

Consistency is good, but I wonder where the need for a strict check comes from.

It should be possible to check with if ( ! term_exists( 'events', 'post_tag' ) ) if a term was not found, unless I'm missing something.

[boonebgorges]

Since [29865], term_exists() has returned null in all cases where no term is found. This is the opposite of what was suggested in 21606.diff​ (which suggests returning 0 in these cases), but it does make return values consistent in case of failure, which is what matters for this ticket.