testTLD incorrectly reports valid TLDs with subdomains as invalid (e.g., a.example.com)

Start with source/fix.common.problems/usr/local/emhttp/plugins/fix.common.problems/include/tests.php and inspect the testTLD function and its current LOCAL_TLD validation. Verify cases such as a.example.com and invalid labels, then confirm that valid labels and the full-length limit are accepted or rejected according to the issue's stated DNS rules.

edit: 100% Copilot-generated. I don't know why it doesn't say that it was authored by copilot, but it was.
edit2: When this is fixed, it's probably worth adding the maximum length check of 255 octets too.

Bug Report

Affected Function: testTLD in tests.php

Problem

When the LOCAL_TLD is set to a value like a.example.com, the function currently splits on the dot and only checks the first label (e.g., a). Since the code enforces a minimum length of 2 for the TLD, any TLD where the first label is less than 2 characters (as in a.example.com) is incorrectly flagged as invalid, even though it is a valid FQDN.

What happens:

• testTLD runs this logic:

  $TLDmain = explode('.', trim($unRaidVars['LOCAL_TLD']))[0];
  if (strlen($TLDmain) < 2 || strlen($TLDmain) > 63 || preg_match('/[^a-zA-Z0-9\-]+/m', $TLDmain)) ...
  

• This only validates the first label of the TLD, not the full TLD or all its labels.
• Inputs like a.example.com cause false positives (invalid warning) even though each label is otherwise valid.

Expected Behavior

• Each label in the TLD (split by .) should be checked against DNS rules:
  • Each label: 1-63 chars, only [a-zA-Z0-9-]
  • Whole TLD: up to 253 chars (DNS)
  • Dots should not be treated as invalid
• No unnecessary warning for valid subdomains like a.example.com

Proposed Fix

Replace this block:

$TLDmain = explode('.', trim($unRaidVars['LOCAL_TLD']))[0];
if (!$unRaidVars['LOCAL_TLD'])
  addWarning(...);
elseif (strlen($TLDmain) < 2 || strlen($TLDmain) > 63 || preg_match('/[^a-zA-Z0-9\-]+/m', $TLDmain))
  addWarning(...);

With:

if (!$unRaidVars['LOCAL_TLD']) {
  addWarning(...);
} else {
  $tld_labels = explode('.', trim($unRaidVars['LOCAL_TLD']));
  $invalid = false;
  foreach ($tld_labels as $label) {
    if (strlen($label) < 1 || strlen($label) > 63 || preg_match('/[^a-zA-Z0-9\-]/', $label)) {
      $invalid = true;
      break;
    }
  }
  if ($invalid || strlen($unRaidVars['LOCAL_TLD']) > 253) {
    addWarning(...);
  }
}

References

• Relevant PHP file and function

Impact

• Users with valid FQDNs including subdomains may see incorrect warnings about invalid TLDs.

Environment

• Bug found in commit: 7056e6e452c27ae690a00f5b2dba1e164de40939

Let me know if a patch or PR is desired!