Error:

Deprecated function: strnatcasecmp(): Passing null to parameter #2 ($string2) of type string is deprecated in Drupal\Core\Layout\LayoutPluginManager->Drupal\Core\Layout{closure}() (line 204 of core/lib/Drupal/Core/Layout/LayoutPluginManager.php)

Solution :

This warning indicates that the strnatcasecmp() method in your Drupal site is receiving a null value for its second parameter. Passing null to arguments that require a string has been deprecated since PHP 8.1. Here are some measures you may take to fix this problem:

Step 1: Locate the Issue:– The warning message points to the problematic code in LayoutPluginManager.php at line 204. You’ll need to examine this line to understand why a null value is being passed.

Step 2: Check the Code:-Open the LayoutPluginManager.php file and go to line 204. It probably looks something like this:

$sorted = usort($layout_definitions, function ($a, $b) {
    return strnatcasecmp($a['label'], $b['label']);
});

Step 3: Debugging:-

Add some debugging code to see which value is null. For example:

$sorted = usort($layout_definitions, function ($a, $b) {
    if (is_null($a['label']) || is_null($b['label'])) {
        error_log('Null value detected: ' . print_r($a, true) . ' ' . print_r($b, true));
    }
    return strnatcasecmp($a['label'], $b['label']);
});

Check your error logs to see which layout definitions are causing the issue.

Step 4: Add Null Checks:

Modify the function to handle null values gracefully:

$sorted = usort($layout_definitions, function ($a, $b) {
    $labelA = $a['label'] ?? '';
    $labelB = $b['label'] ?? '';
    return strnatcasecmp($labelA, $labelB);
});

This code uses the null coalescing operator (??) to replace null values with empty strings before comparing.

Step 5: Patch or Update Drupal:

If this is a bug in Drupal core or a contributed module, look for updates or patches that fix the problem. The Drupal community may have already addressed this issue in a subsequent edition.

Step 6: Review Contributed Modules and Custom Code:

If the issue originates from a contributed module or custom code, apply similar null checks in those areas. Ensure that all code using strnatcasecmp() handles null values appropriately.

Original Code:-

uasort($definitions, function (LayoutDefinition $a, LayoutDefinition $b) {
  if ($a->getCategory() != $b->getCategory()) {
    return strnatcasecmp($a->getCategory(), $b->getCategory());
  }
  return strnatcasecmp($a->getLabel(), $b->getLabel());
});

Modified Code:-

To handle null values, utilize the null coalescing operator (??) to supply default empty strings for comparison.

uasort($definitions, function (LayoutDefinition $a, LayoutDefinition $b) {
  $categoryA = $a->getCategory() ?? '';
  $categoryB = $b->getCategory() ?? '';
  $labelA = $a->getLabel() ?? '';
  $labelB = $b->getLabel() ?? '';
  
  if ($categoryA != $categoryB) {
    return strnatcasecmp($categoryA, $categoryB);
  }
  return strnatcasecmp($labelA, $labelB);
});

Issue Solved.