Decoding HTML Entities

PHP Tutorials - Herong's Tutorial Examples

∟Receiving Non-ASCII Characters from Input Forms

∟Decoding HTML Entities

This section provides a tutorial example on how decode HTML entities received from HTML forms with iso-8859-1 encoding for non-ASCII characters.

As you see earlier in this chapter, if page has "charset=iso-8859-1", Unicode characters will be received as HTML entities in $_REQUEST. How can we convert them back to Unicode characters?

I have tried with "urldecode()" and "rawurldecode()". They work fine on single-byte characters. But they do not work with multi-byte characters.

PHP has a special function "html_entity_decode()" to decode HTML entities with multi-byte characters. Here is the syntax of html_entity_decode():

   html_entity_decode(string[, quote_style[, charset]])

where "string" is the HTML entity encoded string; "quote_style" specifies how quotes should be handled; and "charset" specifies which character set to use. Supported character sets include: ISO-8859-1, UTF-8, cp1251, GB2312, and Shift_JIS.

To show you how to use html_entity_decode(), I modified InputIsoGet.php to InputIsoGetDecoded.php:

<?php
#  InputIsoGetDecoded.php
#- Copyright 2009 (c) HerongYang.com. All Rights Reserved.
#
#- Promoting CGI values to local variables
   global $r_English, $r_Spanish, $r_Korean, $r_ChineseUtf8;
   global $r_ChineseGb2312;
   import_request_variables("GPC","r_");

#- Generating HTML document
   print("<html>");
   print('<meta http-equiv="Content-Type"'
      .' content="text/html; charset=utf-8"/>');
   print("<body>\n");
   print("<form action=InputIsoGetDecoded.php method=get>");
   print("English ASCII: <input name=English"
      ." value='$r_English' size=16><br>\n");
   print("Spanish UTF-8: <input name=Spanish"
      ." value='$r_Spanish' size=16><br>\n");
   print("Korean UTF-8: <input name=Korean"
      ." value='$r_Korean' size=16><br>\n");
   print("Chinese UTF-8: <input name=ChineseUtf8"
      ." value='$r_ChineseUtf8' size=16><br>\n");
   print("Chinese GB2312: <input name=ChineseGb2312"
      ." value='$r_ChineseGb2312' size=16><br>\n");
   print("<input type=submit name=submit value=Submit>\n");
   print("</form>\n");

#- Outputing input strings back to HTML document
   print("<hr>");
   print("<pre>");
   print("Input strings before decoding:\n");
   foreach ($_GET as $k => $v) {
      print "$k = ($v)\n";
   }
   print("</pre>");

#- Outputing input strings back to HTML document - decoded
   print("<hr>");
   print("<pre>");
   print("Input strings after decoding:\n");
   foreach ($_GET as $k => $v) {
      print("$k = (".html_entity_decode($v,ENT_COMPAT,"UTF-8").")\n");
   }
   print("</pre>");
   print("</body>");
   print("</html>");

#- Dumping input strings to a file
   $file = fopen("\\temp\\InputIsoGet.txt", 'ab');
   $str = "------\n";
   fwrite($file, $str, strlen($str));
   if (array_key_exists('QUERY_STRING',$_SERVER)) {
      $str = $_SERVER['QUERY_STRING'];
   } else {
      $str = NULL;
   }
   fwrite($file, $str, strlen($str));

   $str = "------\n";
   fwrite($file, $str, strlen($str));
   foreach ($_REQUEST as $k => $v) {
      $str = "$k = ($v)\n";
      fwrite($file, $str, strlen($str));
   }
   fclose($file);
?>

Now enter the following input strings on InputIsoGetDecoded.php to see what happens:

English ASCII: Hello world!
Spanish UTF-8: ¡Hola mundo!
Korean UTF-8: ???? ?? !
Chinese UTF-8: ????!
Chinese GB2312: ????¡

If you click the submit button, you will get:

Input strings before decoding:
English = (Hello world!)
Spanish = (¡Hola mundo!)
Korean = (???? ?? !)
ChineseUtf8 = (????!)
ChineseGb2312 = (????¡)
submit = (Submit)
------
Input strings after decoding:
English = (Hello world!)
Spanish = (¡Hola mundo!)
Korean = (여보세요 세계 !)
ChineseUtf8 = (仠好世界!)
ChineseGb2312 = (????¡)
submit = (Submit)

The first section shows you input strings as they are received in HTML entity encoding. The second section shows you input strings as they are decoded from HTML entity encoding to UTF-8 encoding.