[wp-trac] [WordPress Trac] #60059: Warning / Error in wp-includes/canonical.php when $_GET['author'] is an array

[WordPress Trac]

#60059: Warning / Error in wp-includes/canonical.php when $_GET['author'] is an
array
--------------------------------------+-----------------------------
 Reporter:  david.binda               |       Owner:  SergeyBiryukov
     Type:  defect (bug)              |      Status:  closed
 Priority:  normal                    |   Milestone:  6.5
Component:  Canonical                 |     Version:  trunk
 Severity:  normal                    |  Resolution:  fixed
 Keywords:  has-patch has-unit-tests  |     Focuses:
--------------------------------------+-----------------------------

Comment (by fudxtrpj14):

 The warning or error you're encountering in WordPress related to the
 $_GET['author'] parameter being passed as an array can indeed be addressed
 with a fix to the `canonical.php` file. This is a known issue, and
 ensuring compatibility with different PHP versions is crucial for
 maintaining the stability and functionality of your WordPress site.

 Here's a breakdown of the problem and how you can implement a fix:

 ### Understanding the Issue

 1. **Parameter Type Mismatch**: The error occurs because the
 `preg_match()` function in the canonical.php file expects the second
 parameter to be a string, but it's receiving an array instead when the
 $_GET['author'] parameter is passed as an array.

 2. **Impact on PHP Versions**: The severity of the issue varies depending
 on the PHP version. In PHP 8+, it leads to a fatal error, while in earlier
 versions, it triggers a warning.

 ### Proposed Solution

 To fix this issue, you can modify the code in the `canonical.php` file to
 handle the case where $_GET['author'] is an array. Here's how you can do
 it:

 ### Step 1: Locate the Code

 The code in question is located in the `canonical.php` file within the
 `wp-includes` directory of your WordPress installation.

 ### Step 2: Add Conditional Check

 Before performing the `preg_match()` function, you should add a
 conditional check to ensure that $_GET['author'] is a string. If it's not
 a string, you can handle the array case appropriately.

 ### Step 3: Implement the Fix

 Here's an example of how you can implement the fix:

 ```php
 // Original code
 if ( is_author() && ! empty( $_GET['author'] ) && preg_match(
 '|^[0-9]+$|', $_GET['author'] ) ) {
     // Perform the necessary operations
 }

 // Modified code
 if ( is_author() && ! empty( $_GET['author'] ) ) {
     if ( is_string( $_GET['author'] ) && preg_match( '|^[0-9]+$|',
 $_GET['author'] ) ) {
         // Perform the necessary operations
     } elseif ( is_array( $_GET['author'] ) ) {
         // Handle the case where $_GET['author'] is an array
         // For example, you can log an error or redirect to a suitable
 page
     }
 }
 ```

 ### Step 4: Test the Fix

 After implementing the fix, it's essential to test it thoroughly to ensure
 that it resolves the issue without introducing any new problems.

 ### Conclusion

 By adding a conditional check to handle the case where $_GET['author'] is
 an array, you can prevent the warning or error from occurring in
 WordPress, ensuring compatibility across different PHP versions. It's
 advisable to keep track of such issues and apply appropriate fixes to
 maintain the stability and security of your WordPress site.

-- 
Ticket URL: <https://core.trac.wordpress.org/ticket/60059#comment:9>
WordPress Trac <https://core.trac.wordpress.org/>
WordPress publishing platform