Decoding numeric html entities via PHP

Question

I have this code to decode numeric html entities to the UTF8 equivalent character.

I'm trying to convert this character:

’

which should output:

’

However, it just disappears (no output). (i've checked the source code of the page, the page has the correct utf8 character set headers/meta tags).

Does anyone know what is wrong with the code?

function entity_decode($string, $quote_style = ENT_COMPAT, $charset = "UTF-8") {    
     $string = html_entity_decode($string, $quote_style, $charset);

     $string = preg_replace_callback('~&#x([0-9a-fA-F]+);~i', "chr_utf8_callback", $string);
     $string = preg_replace('~&#([0-9]+);~e', 'chr_utf8("\\1")', $string);

    //this is another method, which also doesn't work.. 
     //$string = preg_replace_callback("/(\&#[0-9]+;)/", "entity_decode_callback", $string);

     return $string; 
}




function chr_utf8_callback($matches) { 
     return chr_utf8(hexdec($matches[1])); 
}

function chr_utf8($num) {   
     if ($num < 128) return chr($num);
     if ($num < 2048) return chr(($num >> 6) + 192) . chr(($num & 63) + 128);
     if ($num < 65536) return chr(($num >> 12) + 224) . chr((($num >> 6) & 63) + 128) . chr(($num & 63) + 128);
     if ($num < 2097152) return chr(($num >> 18) + 240) . chr((($num >> 12) & 63) + 128) . chr((($num >> 6) & 63) + 128) . chr(($num & 63) + 128);
     return '';
}

function entity_decode_callback($m) { 
     return mb_convert_encoding($m[1], "UTF-8", "HTML-ENTITIES"); 
} 

 echo '=' . entity_decode('&#146;');

Answer 1

The PHP function mb_convert_encoding() already does what you're looking for:

$string = '’';

echo mb_convert_encoding($string, 'UTF-8', 'HTML-ENTITIES');

it works a little bit better than html_entity_decode() that also does what you're looking for, but it may not have support for all numeric entities (see below):

$string = '’';

echo html_entity_decode($string, ENT_COMPAT, 'UTF-8');

It will return the character:

’   binary hex: c292

Which is PRIVATE USE TWO (U+0092). As it's private use, your PHP configuration/version/compile might not return it at all.

Also there are some more quirks:

But in HTML (other than XHTML, which uses XML rules), it's a long-standing browser quirk that character references in the range € to Ÿ are misinterpreted to mean the characters associated with bytes 128 to 159 in the Windows Western code page (cp1252) instead of the Unicode characters with those code points. The HTML5 standard finally documents this behaviour.

See: ’ is getting converted as “\u0092” by nokogiri in ruby on rails