Address HTML entity mbstring deprecation

[ssddanbrown]

Found during testing for PHP8.3 (but relevant since PHP8.2).
Deprecation notice:

mb_convert_encoding(): Handling HTML entities via mbstring is deprecated; use htmlspecialchars, htmlentities, or mb_encode_numericentity/mb_decode_numericentity instead

This applies to a couple of places where we use this kind of pattern:

        $doc = new DOMDocument();
        $doc->loadHTML(mb_convert_encoding($html, 'HTML-ENTITIES', 'UTF-8'));

This converts UTF8 chars to HTML entities first, so UTF8 characters are retained no matter the output encoding. PHP won't load this as UTF8 unless a specific encoding is set within the loaded content. Setting the DOMDocument itself to UTF8 upon load won't help as it's overridden on the ->loadHTML() call.

Just throwing on '<?xml encoding="UTF-8">' can somewhat mangle the output depending on input (if partial or full HTML fragment).

Need to standardise proper handling depending on what's expected as input/output.
A good point to fully align (and centralise?) general high-level HTML handling maybe, therefore deferring to a full release.

[ssddanbrown]

DOMDocument Usages

This is a little audit of DOMDocument usages within the app.

app/Entities/Tools/PageContent.php

• Loads text as UTF-8 via new method already.
• Loads text as partial HTML (page content).
• Used for:
  • Searching for and extracting base64 images
  • Finding and extracting specific page sections (includes)
  • Formatting upon page save (Apply IDs and Fix links)
  • Loading page navigation
• Returns:
  • Specific text/attribute values
  • All inner nodes loaded (in body)
  • Specific inner sections

app/Entities/Tools/ExportFormatter.php

• mb_convert_encoding used.
• Loads text as entire page HTML
• Used for:
  • Opening detail blocks (apply open attr)
  • Replacing Iframes elements with links
• Returns:
  • All nodes

app/References/ReferenceUpdater.php

• mb_convert_encoding used.
• Loads partial HTML (page content within body)
• Used for:
  • Updating link attributes
• Returns:
  • All inner nodes loaded (in body)

app/References/CrossLinkParser.php

• Loads text as UTF-8 via new method already.
• Loads partial HTML (page content within body)
• Used for:
  • Getting links within content
• Returns:
  • Array of link attribute values

app/Search/SearchIndex.php

• Loads text as UTF-8 via new method already.
• Loads partial HTML (page content within body)
• Used for:
  • Parsing all text from content
• Returns:
  • Map of numbers by text term

app/Util/HtmlNonceApplicator.php

• Loads text as UTF-8 via new method already.
• Loads partial HTML
• Used for:
  • Applying attributes to elements
• Returns:
  • All inner nodes loaded (in body)

app/Util/HtmlContentFilter.php

• Loads text as UTF-8 via new method already.
• Loads partial HTML
• Used for:
  • Removing nodes and attributes
• Returns:
  • All inner nodes loaded (in body)