PHP Deprecated Warning: mb_convert_encoding function

Issue: In recent PHP versions, developers may encounter a warning indicating that handling HTML entities via mbstring with mb_convert_encoding() is deprecated. Specifically, using mb_convert_encoding() to convert HTML to UTF-8 encoding with the HTML-ENTITIES flag will trigger this deprecation notice:

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

This issue arises when mb_convert_encoding() is used to encode special characters as HTML entities to ensure compatibility with DOMDocument or other functions that require valid HTML.

Cause: The HTML-ENTITIES flag with mb_convert_encoding() has been marked as deprecated because more specific functions are available for handling HTML entities directly.

Solution: To address this, you can replace mb_convert_encoding() with a combination of htmlspecialchars, htmlentities, or mb_encode_numericentity depending on your requirements. Below are some alternative approaches:

1. Using `htmlspecialchars` (Best for Basic HTML Content)

If your content includes simple text with few special characters, htmlspecialchars can be a straightforward replacement. This function converts special characters to HTML entities, making the content safe for HTML.

// Convert special characters in HTML content to HTML entities
$safeContent = htmlspecialchars($content, ENT_QUOTES, "UTF-8");

2. Using `htmlentities` (More Comprehensive Entity Encoding)

If your content includes a broader range of characters that might not render correctly in HTML, use htmlentities. This function encodes a larger set of characters as HTML entities, ensuring compatibility with DOMDocument and other HTML parsers.

// Convert all applicable characters in HTML content to HTML entities
$safeContent = htmlentities($content, ENT_QUOTES, "UTF-8");

3. Using `mb_encode_numericentity` for Custom Encoding (Best for Non-ASCII Characters)

For cases where you need to preserve HTML tags but still encode non-ASCII characters, mb_encode_numericentity is a good choice. This function allows you to encode only specific character ranges as numeric entities, leaving HTML tags intact.

// Define character range for encoding non-ASCII characters as numeric entities
$map = [0x80, 0x10FFFF, 0, 0xFFFF];

// Convert non-ASCII characters to numeric entities
$safeContent = mb_encode_numericentity($content, $map, "UTF-8");

This approach ensures compatibility with DOMDocument and other parsers without breaking the structure of HTML tags.

Summary

Use htmlspecialchars when you need basic HTML encoding.
Use htmlentities for more comprehensive character encoding in HTML.
Use mb_encode_numericentity when you need to encode specific character ranges without altering HTML tags.

These alternatives provide greater flexibility and compatibility, allowing you to handle HTML encoding safely and effectively without relying on mb_convert_encoding() with the HTML-ENTITIES flag.