[wp-trac] [WordPress Trac] #64864: previous_posts(): PHP 8.1 deprecation notice

[WordPress Trac]

#64864: previous_posts(): PHP 8.1 deprecation notice
--------------------------------------------+------------------------------
 Reporter:  dd32                            |       Owner:  SergeyBiryukov
     Type:  defect (bug)                    |      Status:  closed
 Priority:  low                             |   Milestone:  7.0
Component:  Themes                          |     Version:
 Severity:  trivial                         |  Resolution:  fixed
 Keywords:  php81 has-patch has-unit-tests  |     Focuses:  coding-
                                            |  standards
--------------------------------------------+------------------------------
Changes (by SergeyBiryukov):

 * owner:  (none) => SergeyBiryukov
 * status:  new => closed
 * resolution:   => fixed


Comment:

 In [changeset:"62034" 62034]:
 {{{
 #!CommitTicketReference repository="" revision="62034"
 Code Modernization: Fix "passing null to non-nullable" deprecation from
 `previous_posts()`.

 The `esc_url()` function expects to a string for `$url` parameter. There
 is no input validation within that function. The function contains a
 `ltrim()` which also expects a string. Passing `null` to this parameter
 results in `Deprecated: ltrim(): Passing null to parameter #1 ($string) of
 type string is deprecated` notice on PHP 8.1+.

 Tracing the stack back, a `null` is being passed to it within
 `previous_posts()` when `get_previous_posts_page_link()` returns `null`
 (it can return a string or `null`).

 On PHP 7.0 to PHP 8.x, an empty string is returned from `esc_url()` when
 `null` is passed to it. The change in this changeset avoids the
 deprecation notice by not invoking `esc_url()` when
 `get_previous_posts_page_link()` returns `null` and instead sets the
 `$output` to an empty string, thus maintaining the same behavior as before
 (minus the deprecation notice).

 Adds a test to validate an empty string is returned and the absence of the
 deprecation (when running on PHP 8.1+).

 Follow-up to [9632], [11383], [56740].

 Props dd32, alexodiy.
 Fixes #64864.
 }}}

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Ticket URL: <https://core.trac.wordpress.org/ticket/64864#comment:3>
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