Regex in add_rewrite_tag not accepting OR operators?

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I am trying to add a custom field to the post permalinks by using a combo of add_rewrite_tag and applying a post_link filter.

What I am aiming for is something like this: 

http://example.com/%category%/%mycustomfield%/%postname%

I can manage to get the %mycustomfield% as %psubject% working by using 

add_action( 'init', 'register_rewrite_tag');
function register_rewrite_tag() {  
    add_rewrite_tag( '%psubject%', '(.*)' );
}

However there are only a set number of %psubject% values.

But the regex below, which I have tested on regex testers does not work and instead redirects all posts with this link structure to the homepage as home.php, not even a 404 or index redirect. 

add_rewrite_tag( '%psubject%', '(option1|option2|option3)');

However simply having the regex inputs below will work. 

(option1) or (.*)

Such as 

http://example.com/somecategory/option1/this-is-the-post-title

will show the correct post.

Edit: I have found even in WordPress 3.6 that this issue still occurs.

It appears that by using the regex OR operator in the add_rewrite_tag function only will allow the last option of the OR statement, but not any before it.

Example:

add_rewrite_tag( '%slugname%', '(orange|apple|strawberry)');

Will only allow ‘strawberry’, despite the syntax being a standard OR statement.

This issue does not occur in other WordPress functions such as add_rewrite_rule.

Question: How can I tell the rewrite tag to only allow a set number of strings to be accepted for the permalink?

1 Answer
1

I don’t know what’s wrong but I can suggest:

  • Use Rewrite Rules Inspector or similar to see where your %psubject% rule is and if its pattern ((option1|option2|option3)) has been added correctly.
  • Test http://example.com/somecategory/option1/this-is-the-post-title with the Inspector to see which rule matches.
  • Open http://example.com/somecategory/option1/this-is-the-post-title (when it shows home.php) with the Debug Bar plugin and look at Query String, Matched Rewrite Rule, and Matched Rewrite Query.

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